Diablo 3 is indeed a very well optimized game and runs without any problem on low end hardware. I manage to squeeze up to 55 FPS on low settings at 1280x720 with my Intel HD 3000 Graphics equipped laptop (Core i3 2310m CPU and 8 GB RAM), which is more than enough. I have played a lot with the video settings, but it was well worth it, as now the game runs perfectly smooth without any lag or overheating issues. I have written an article that explains the different Diablo 3 video settings and recommends the optimal ones for Intel HD Graphics and other low end video cards. If you are interested, you can check it out on my blog:
9.5 for Diablo 3 score absolutely ridiculous. Totally makes sense though, once you realize he gave out the score without even finishing the game. "hint: he never even played in inferno mode" http://diablo3goldfarmen.com
Diablo 3 runs quite nicely with Lenovo W520 (2860QM & Quadro 2000M) at 1920x1080 max details. Experience is not exactly butter smooth and lowering details doesn't really help so playing at max. With 4 players in group fps is good enough to enjoy this title fully.
Runs little bit better on my desktop Q9500 & GTX460M where fps is almost constant 60.
I play on my Intel i5 with HD integrated graphics. (4GB ram) I run on the lowest res widescreen, with all settings on low/off, and extra FX off. It isn't the best framerate (prob 40s), but it is definitely playable. Great job to Blizzard devs who made this work on my laptop! The art is so great, that once you are immersed in the game, the low quality settings don't even phase you.