Ok, this title is a little bit misleading, because I never really planned on buying Diablo 3. I'm a fan of the genre, but I prefer to have my hack-and-slashes deep like Baldur's Gate, Neverwinter Nights, or a good old roguelike. Also, the content is often a little iffy, and I bought Starcraft 2 and didn't exactly fall in love with Blizzard from it, and I'm not sold on a new game from them (also, I never played the originals).
But the real reason I'm categorically excluded from playing it is the DRM. Here's why: A while back I bought a game on OnLive. I enjoy OnLive, and don't mind using their service. However, recently I've been experiencing lag spikes where I go for well over a second without game-playable levels of connection. This means that if I were playing my OnLive games, I'd be streaming them and I'd have issues due to my temporary disconnection. I don't mind this for OnLive, but I paid less for my games on there than I would elsewhere (they hooked me with a $1 sale, which is pretty good for the AAA-grade game I got). Also, I've been playing on a laptop, and before I figured out how to optimize it for gaming, it was kinda iffy. Also, saving hard-drive space was nice.
Diablo 3, on the other hand, seems to install all of its game data to the player's computer (though I'm not familiar with its method, but I doubt Blizzard streams it). What I can tolerate in OnLive's service is intolerable in something that's eating up several gigabytes of my hard drive, burning through my GPU, and taxing my CPU and RAM. It's glorified DRM, and it's just not cool in the slightest. This is part of the reason I'm an "indie" gamer increasingly; I prefer a game that I can put on my hard drive and know how it's going to handle. I mean, I'm not a fan of DRM, but I acknowledge that it's legitimate, even if I feel it's useless compared to increasingly sophisticated pirates. Streaming all the play data for a single-player game? What if I want to cheat at my games, becoming a demigod striding through the battlefield watching my foes fall before my avatar's mighty onslaught? What if I wanted to modify the game to play it as a space opera, western, or cyberpunk adventure?
I'm not stating that my games have to be built with cheats and mod compatibility, but look at Skyrim and see how successful it is. My purchase of it relied on the fact that I knew I could change stuff I didn't like about it, or install tweaks others made to make it more interesting. Blizzard, I'm not going to buy your game if I can't root around in the data files to try to see how stuff ticks and try to give myself a new shiny without you revoking my license or change a couple bytes of memory to make myself a fearsome warrior. It's not a matter of whether or not I would, it's a matter of principle. If I'm buying a game, I want to have it run on my computer; I'll buy Avernum before I buy Diablo any time, and not just because I prefer the former's in-depth gameplay and charming setting and graphics. I'll buy something that's the whole package, not merely a client to connect to a server.