...youre both being a jerk and selling me short.

I KNOW the perk exists...but just like the shotguns in Fallout New Vegas I SHOULDNT have to spend a perk just to make something useless worth a damn!

Bad design cant be excused by putting on your best "Special School Teacher frustrated at all the retards they have to deal with" face!

You don't have to use the perk. But as you've noticed, it means that you have to be very tactical about how you use the Invisibility spell. Much like you can't just cast any other spell from hiding without being noticed if you don't have that perk.

I can understand arguments against perks that solely increase damage, etc., but arguing against a perk that actually provides an incentive for getting it? That's just ridiculous.

Well your post that I was responding to is about how invisibility is loud and gets you detected. If you know the solution then why post as if you don't? All spells make noise unless you have silent casting. Ever tried casting mage armor within earshot of enemies? I don't understand how this is bad design, seems things are working just like intended.

If you don't want to spend the perk for silent casting, that is fine, but that is basically a requirement of the spell. Yes it costs perks, but it is superior to any other method of stealth if you combine it with muffle. With invisibility and muffle together and you can freely sprint everywhere you want and drop into sneak mode just for the hits, cut combat at any time, and the only way for you to be detected is if the enemy physically touches you.

Enemies in this game detect with:
Line of Sight
Sound
Touch

Invisibility removes line of sight. Sneak only helps you hide, but you can still be found out by LOS.
Sound is fixed with muffle.

If you use both they cannot detect without an actual touching of your character. No other power completely removes LOS. even shadow warrior (which costs a larger perk investment than silent casting) does not remove LOS beyond that second where you get the invis from crouching, you will still be visible afterwards.

I would say kinda. It is very powerful and has almost no match in the game. It makes being sneaky very, very easy. However wheter it is cheap or not isn't really important. What I think is important is wheter it takes away from your experience or not. If you have fun while using it go for it. If not then don't.

And don't worry to much about your friends opinion on the matter. Skyrim is made so you can decide how you play

It was worse in oblivion. Not to mention chameleon

Here is my roleplaying response: A pure assassin should be using invisibility only from potions because spell casting is not something assassins do, unless they are nightblades. Assassins are well known for brewing powerful poisons, so it is not much of a stretch to imagine them also brewing up a potion of invisibility to be used in a particularly tough spot. So for my Khajiit, he perked both sides of the sneak tree and also perked alchemy but won't use a spell for invisibility.

For my Dunmer nightblade, he perked only the right side of the sneak tree. A nightblade is expected to use spells to move unseen and unheard through the night until you feel death's cold grasp wrap itself around your throat, from out of nowhere he strikes, and then disappears again into the night.

Now, from a gameplay perspective, you need three things to walk unseen among your foes using magic: Invisibility, Muffle and Quiet Casting. You had to make a fair investment to get these, and using them is certainly no more cheap than lots of other stuff in the game like Shadow Warrior, Smithing/Enchanting/Alchemy, etc.

I have just recently started using invisibility with my Dunmer nightblade. The way invisibility works in Skyrim is much more interesting than Oblivion. Invisibility by itself is pretty useless because enemies hear you so well. You need to combine it with Muffle for it to work very well and you need to be sneaking. If you are getting your muffle with a spell instead of a perk or an enchant, it is more challenging because you have to pay attention to whether your muffle is still going. Last night I used invisibility to escape in a situation where I was surrounded by bandits, but my muffle had gone down. The invisibility did not help at all and all the bandits chased me down pretty quickly. Also, if the NPC has a high sneak spell, they can track you down even if you have a muffle going. There is a lot of depth to invisibility in Skyrim and there is enough other stuff I complain about that I would like changed in Skyrim, I thought I would give Skyrim some kudos for the improvements made to the way invisibility works.