I don't get all these people wanting early access. Why spoil yourself on a buggy, feature-incomplete version of the game when you could just wait and get the finished experience when it comes out?
Here’s my personal answer/opinion:
I pledged for this game and early beta because I always loved the IE style games. They made me feel part of that “world” and I liked the art and the gameplay.
I have a feeling (and I might of course be disastrously wrong) that if Obsidian manage to make this thing work, they might have a successful IP, that will turn out to be popular, with a decent-sized group of modders and a community of people dedicated to keep this thing going.
Basically, we could get something like what NWN/NWN2 community could/should have been, but without the shitty engine. Imagine new adventures for IWD2/BG2 style games that come out (mostly for free!) every three months or so. Imagine being able to play a whole new adventure with your BG2 or IWD2 characters, in different settings and different parts of the world.
Not just mods for resolution and bugfixing, but whole new “modules” a la NWN, only without NWN’s shit engine. Modules you could actually enjoy!
I am therefore willing to work for free and even pay a fee to help debug this game, and its engine. I might not enjoy the finished product as much as I would if I only played once it came out, but I haven’t enjoyed things since 2004 anyway, so who cares.
edit
i didn't pledge for torment's early access (i don't even know if there was one) because in that case i want to enjoy the story. priorities, preferences...