As someone who wasn't a particularly big fan of the previous two Diablo games, I was a little skeptical about this one. However, I received a digital copy for free from Blizzard via the World of Warcraft Annual Pass subscription. I had become interested in some of the pre-release teaser videos, but they could not possibly prepare me for the game I was about to play.
After the initial launch day hiccups (bad form, Blizzard...) I fired up the game for the first time and was immediately hooked. Five hours passed without my notice. I hadn't experienced pure joy in a video game like this since I was fifteen years old. I've tried out a couple of the different classes, and it's incredible how much depth there is to this game. Every class plays differently, and there are at least three or four possible skill builds for each class, which you'll have plenty of fun toying around with due to a fine-grained system that unlocks your abilities gradually, and then unlocks skill runes that can be applied to each skill, some of them changing the base skill until it's almost unrecognizable. There are thousands of combinations, all at your fingertips and all changeable in seconds.
People will ding the game for its always-online DRM. They'll ding it for the launch day shenanigans. They'll call it "dumbed down" or shallow or not as good as Diablo II. Some of those are good points, others aren't. The fact is that it just doesn't matter. Taken on its own merits, Diablo III is an intensely enjoyable experience that will keep you occupied for a very long time. I highly recommend it.