Sometimes I could definitely use a little extra poison damage in tough fights, but in almost every one of those fights, the enemy is immune: high level draugr, vampires, etc.

Do you guys find alchemy to be a useful investment of perks? If so, why? How do you use it? How many, and which perks do you take?

Disclaimer: I am not saying alchemy is not useful, I am trying to decide whether or not to sink perks into it.

Slow poison, paralyze, fortify (anything), elemental resistances, fear, frenzy, restore health, magic, stamina....ya it's worth it...not to mention the $$ making potential of it....

Its a yes and no type of answer in my opinion. Yes its useful and no I don't put perks into it.
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Yes its useful in the sense they give plenty of money, early on in my Master playthrough I take all the potions I can get a hold of which includes either stealing, finding, or making.

I don't invest it in simply because I don't have to. I find/buy enough ingredients to make a large quantity of potions that I have no real need for it. My armor rating takes a good chuck of damage, my blades deal enough damage, my shouts help in large groups, and after some time poisons don't do enough.

Is there a reason you say "slow poison", instead of just "poison"?

So far it seems fairly underpowered to me, but I haven't really tried hard to get the most out of it.

The main problems that seem to make it hard to get much power out of it:
1. it seems to level pretty slow overall
2. with lowish speechcraft, you don't actually make that much, though that changes pretty quickly as your alchemy and speed skills get into the 30s. I imagine in the 50s it is insanely lucrative.
3. Alchemy is an inherently 'support' skill. You can use it to support just about anything, but you've got to be good at something else for it to be an effective 'adventurer skill' it would seem. You can't just have ~60 Alchemy with a 75% perk tree and 15s and 20s in nearly everything else and go galivanting wherever you want in Skyrim. You're probably gonna die, else have to run a way a LOT. This effectively means that leveling in alchemy to gain 'power' is half or even a third or a fourth as fast as leveling in some more direct form of adventuring prowess.

All of which leads me to conclude: at middle-highish skill levels, having kept up a bit of advance in alchemy could well pay off dividends. But early game to early-middle game it is an understated craft.

Seems a pretty good balance to me.

In Oblivion, I was always thinking to myself as I was churning away at potions while kneeling in a stinking filthy sewer in pitch blackness . . . "Now waitaminute! If its this easy to gain power from making potions, then why isn't EVERYONE doing it!?"

Alchemy's primary value is making insane amounts of money.

And some of the potions you can make are pretty decent, too. Especially if you're a Destruction mage facing a difficult fight; only potions can make your Destruction more powerful.

I think the biggest problem is that potions are poisons are so clunky to use. They always have been. If there was a way to set a hotkey for using potions or applying poisons (maybe something akin to the belt system in Diablo II) it'd be easier to use, and therefore more useful to me.

On top of that, I normally find so many potions laying around anyway, that I never really felt the need to use it.

Yes, alchemy is incredibly potent. And not just for poisons, which I never use anyway because I never remember. Besides, why use a poison (which doesn't work on numerous enemies) when you can instead use alchemy to make your weapons more powerful through fortify smithing? That is what I use it for, plus healing and magicka potions. With 5 power perks plus benefactor and +100% fortify alchemy apparel you can fortify smithing by 120%. That is way more useful than poisons IMO.

I admit, I have not been using poisoned arrows like I did on Oblivion. I used a poison on my sword once but I hope that the poison effect can last for a few hits. Like you dip several arrows per bottle instead of using a whole bottle of poison for just one arrow.

Yes, I rarely use damaging poisons, but slow poison I use extensively. Try enchanting a bow with just one point of frost damage (which with a grand soul and no perks and lvl 15 enchant will give you over 1000 charges) and hit someone with a slow poison....they will crawl towards you

There must be some mod to make using poisons less clunky. I use More Hotkeys Please. Will have to check if you can assign a hotkey to poisons and use that in combat. Only problem there is the hotkey would reference a specific poison, so if you didn't have a lot of one type that stacks in your inventory, even that would be only an interim fix. You'd have to set a new hotkey when you ran out of that type poison.