It depends really. If you liked d2 then I wouldn't even consider it.
Now if you like the games predecessor, World of warcraft, then I couldn't recommend it enough. They really incorporate wow lore into this to put you in the mood to play wow.
I, on the other hand, am fat. I got the game so I'd get out of the house more. I'll tell myself something like "if you quit now you have to play d3 when you get home". Imo it's a game changer in the cardiovascular scene.