Well recently my thief character has become a vampire, and there are a lot of mods out there to change that experience. Right now I'm using ParasiteX's Vampire mod. It's alright, decent amount of abilities, aging, etc. The lack of magicka regen does drive me a little crazy though. You never notice how much even your non-mage character uses magic till you're bound to potions forever to fuel it. I've also tried StarX's Vanilla Vampire overhaul, but eh...it's not so much a vampire overhaul for the player as it is one for the NPCs of the world. Are there any well-developed Vampire mods released out there with a lot of features? I'm not really sure what to use because a lot of them sound similar or are based off the same Kiyoshi (I think that's who it is?) mod.

I did see that there's a mod in the works here, Unholy Darkness, which sounds great so far, though not released yet. Anything that could tide me over the in meantime?

Try out http://www.tesnexus.com/downloads/file.php?id=28926... It's a little buggy but still effective. And fully customizable
You can try http://www.tesnexus.com/downloads/file.php?id=6492 too. An unusual vampire mod with quests and "classic" vampires, and fully compatible with other vampire mods because it does not use the "conventional" vampirism system.

If you're paitent, Unholy Darkness appears to be nearing completion. You'd have to cure yourself of Vampirism and then load his mod it looks like, due to the way it handles Vampires.

LTD Vampire Overhaul. Enough said.
But make a save before you cure it because I have heard a lot of good things about Unholy Darkness.

The Vampire Experience sounds more like what I'm looking for, actually. How buggy is it? I could just switch over to this mod and use it till Unholy Darkness comes out.

The latest version should be reasonably stable; but please be aware that, at the present time, it is a "discontinued Mod", which means issues/bugs are not likely to be patched/fixed, and no significant support can be provided. Feel free to check the thread here on the forums (it's probably buried at the moment) to find out what other's have said/reported

Quick question about it, do I need to cure myself and re-catch Vampirism for Vampire Experience, or is it okay to just revert back to vanilla vampirism, then install it?

I think just revert back and install. Im not sure.

I'd say wait for Unholy Darkness.

If you haven't read about it, go ahead. The topic is at the top of the page

TVE should auto-detect your Vampirism and convert you. Save before trying, if you're going to use it, just incase, though And I agree with Dante-- Madmole's mod sounds like it's going to be great

Hmm, I seem to have run into a bit of a problem. It successfully identified me as a vampire, got the amulet and everything, but none of the hot keys are working. And since I can't feed the regular way by "activating" people I am unable to feed at all.

Hmm, odd... Are you using OBSE? If not, try the latest version, and see if it helps

Yep. I think I fixed it, I had to use the amulet to become a vampire even though I already was one. It must distinguish between a mod vampire and a vanilla one. Started a new game anyway to clear some old mods out, so that should iron out any difficulties in itself.