On my latest playthrough I've gotten to NV, and realised with how I see the character I've yet to use any armour, and no DT clothing either, or defensive chems.
Combined with the fact that I'm still leveling, and not put any points in sneak, or perks that boost DT, and using close ranged semi / single / lever weapons.
I'm still suprised that I've taken less damage and resolved fights alot quicker than most characters that I've played with at least some of the above, if not all.
I've played heavy 30+ DT and mid DT, but no DT seems to free up alot of room and makes me think how to resolve a fight depending on my foe's, and avoid getting exposed.

So I'm just wondering on others experience and play styles, is defense or at least a high one more a hinderence for you.

I play stealth characters. Reinforced Leather for most of the game. If I'm going into a f'ng irradiated hellhole of a vault then it's the Mk II Combat Armor because stealth means absolutely [censored] in places like Vault 34. I never use armor that reduces any SPECIAL.

Bounty Hunter Duster, Implant and 2x Toughness for a total of 16DT is all I need most of the time.

I never bothered with armor and DT. I dress to look good. Usually a duster or casual clothing. My best defense is a fully upgraded sniper riffle, VATS, Critical perks and some sneak. It solves pretty much everything in a click.

The current one has like 20 DT but that's only because it's an explosives character.
On the other ones I have like at most 8 in DT.

I played a sniper in my first round and I did good against everything not indoors. I barely had any DT at all.

I am wearing the space suit right now, and am perfectly happy. I might even skip power armour (although I kind of need the +2 str to supplement my pathetic str 4).

I am yet to play a character that wears anything more than combat armor... Including my melee specialist... The Power Armor I've found (thankfully minimal) has always gone onto my companions or on display in a safehouse.

I've yet to try playing a character without armor, it just seems like a bad idea to go into combat without any kind of protection to me. Still, I might one day try not using any armor, or at least limiting myself to light armor, just for the sake of trying it if nothing else. Probably with a stealth oriented character, something which I've yet to try. I've made unarmored characters in both Morrowind and Oblivion and enjoyed it, I've never felt inclined to do so in Fallout before though.

Although I've yet to wear power armor, but I never really intended to with my first character, I kind of created my second character under the assumption that I'd eventually want to do so, though, but having yet to pick up any power armor or recieve power armor training, that is, obviously, not yet possible.

The 20% bleed through effect pretty much destroyed the entire concept of DT. In practice it works exactly the same way as DR in FO3.

Get hit for a damage value that's at or below your DT. You lose zero health yet the armor takes all the damage to it's item HPs. How something so simple could be screwed up so badly is beyond me.

So far, I've played on normal. I may increase that, at some point, just because the game can be played so many different ways.
My first character run had an incredibly high DT compared to how I am used to playing RPG's. I took Toughness twice, got the Subdermal implant and when I was going into a rough fight, I used power armor. The battle for the dam became a bit of a slugfest. I probably used 30 stimpacks all told during that, but my build wound up more of a tank than someone who actually causes damage. I didn't take any of the perks that increase your damage, or crits, so even with an AMR and 100 in guns, I took two headshots to kill deathclaws on occassion. Hell, I had a few require 3-4 shots, and the alphas... they were more like 5-7. Grant, I wasn't using appropriate rounds, but still... So I could take an enormous amount of abuse, with a DT around 42+, but my agility was too low to give me the perks to increase my damage. Hell, there were times that I felt like my guns were half broken, even though they were fully repaired, simply because of DT and the fact that I didn't use specialized ammo through most of the game.
My current play through, I'm a smooth talker. I got my guns skill to 30, and there's where it will stay. This character will never use power armor, and often lets Boone take care of combat. Her DT is either 8 or 10. So far, speech, science, barter, etc. have kept the character moving forward. Not sure what I'll do when I run into the vaults though.

For me, DT is king. Heavy, heavy, heavy armor gives me the option of coming out of cover to get the perfect shot lined up. It means that when the enemy gets off a lucky grenade throw, or sudden lunge, that I'm still standing. And it means that when I enter nightmares like Vault 34, my real concern is my Rad-Away supply.

Of course, I'm also not a twitch-gamer anymore. Gone are my days of dodging everything in Doom, and I don't really miss them. DT definately allows me to adopt a patient, methodical way of handling things that combines nicely with my proclivity for blowing limbs off, and occasional use of heavy automatic weaponry.

Plus, T51-b is THE Fallout armor.

I play differently depending on how durable the character is -- more "in your face" with two levels of Toughness, more "shoot first and ask questions later" with lots of action points and crit chance. I tend to wear 0-4 DT clothing no matter what, based on what I think fits the character:

Handyman/RobCo/Vault Utility Jumpsuit on my Energy Weapons/Science/Repair guy...
Merc Grunt Outfit/Ranger Casual Outfit/Ranger Red Scarf Outfit on my Guns/VATS guy...
Grimy Pre-War Business Suit/Jailhouse Rocker/Viva Las Vegas on my Unarmed (Elvis Presley) guy...
Raider Badlands Armor/Great Khan Simple Armor on my evil Melee gal.

I never wear armor that slows walking speed, though, except in the last battle of the game. I hate feeling slowed down.

I actually like it as it is. At first I though the 20% leak was bull as well but it allows me to deal with some random enemies that I randomly encounter without being a walking weapons platform.

I rarely use armor or perks that increase toughness but balance it by playing on normal. I like having to deal with limb damage etc. I also never medicate while in "Danger". It's pretty fun.

I'm only tempted into wearing armor occasionally if it looks cool but only for a short span.

I'm with these guy's

Been loving http://www.newvegasnexus.com/downloads/file.php?id=36615 on my two main characters, a Melee/Unarmed and an Explosives/Energy. The melee guy is based on a lightning/thunder-themed D&D character of mine, and the Demo Expert needed something black and metal, so it's perfect.

• Non Faction T51-B armor
  
• Recon Helmet
  
• Authorotay Sunglasses
  
• Sub Dermal Implant
  
• x1 Toughness Perk
  
• Silent Running Perk

I switch to Dapper Gambler outfit, sunglasses and one of the Prewar or Gambler hats when I'm in the Vegas Strip
Earlier in the game I use the black VanGraff variant of the combat armor and either the MKII Combat Helmet or the 1st Recon Beret and Sunglasses
I'll likely switch to the Remnant or Tesla Armor once I get to it in the game...

I am on the same boat. Since the only thing DT>20 would have impact against is Trail Carbine, yet there isn't a large mob of them (unless you are hated by NCR),

20% bleed through is the only saving grace back before the update remove double DT from creatures.

So low DT and sneak is favoured as a style, what about running and gunning?
Sneak its self is pretty defensive, and the slower ROF combined with slow movement and flexibility for one instant kill against a foe, given enemy fire when crouched tends to hit the head.
That even with a silenced weapon will spark off enemies radar, and everything comes in groups in NV, meaning only very long range kills will offer much protection.

A character that moves from cover to cover with a semi automatic, single action weapon can crouch to steady aim when needed, back peddle when facing melee critters.
Close to gain steady accurate fire from higher damage weapons, and with a scoped or even unscopped rifle cause a sneak crit without bumping up sneak at long - mid ranges.

Its most likey my playstyle as I tend to be impulsive, but even though I'm taking higher damage fom low level npc's, most creatures have attacks that ignore DT.
Especially high end ones, and cazadors, death claws and night stalkers have a high detection rate, come in numbers and cazadors at least flit arround too fast to draw a bead on.

The one part I guess DT can come in handy with, would be the last quest, but so far out of 7 or so characters light armour and perks seem to offer the best physical protection, and don't limit speed.