Well, I'll try to make the necro worth something.
I bought Reaper of Souls a few weeks ago, booted Diablo 3 again and found a way better game than I remembered. The progression is very fast, difficulty is tunable, so no more grinding through trivial difficulties before getting to the main game. Useful items drop all the time, with a nice number of legendaries sprinkled in that nudge the player towards interesting character builds. There's a lot of new things to go for and Adventure mode is a diverse way of going around killing monsters.
And by progression is fast I mean that my first character in the old D3 took 60 hours to get to level 60. The new one I rolled for RoS took 14 hours to get to level 70 and it was suitably challenging all the way through. Also, after beating Act V with any character, there's no reason to go through the main storyline again to hear what must have angered the goat men or whatnot.
This time I also got geared for the late game for the first time, which was surprisingly not-painful.
Oh yeah, there's also a ladder/season thing now, that doesn't really matter, but it gives a fresh start and there's double the achievements to earn, which is sort of fun.
The base game was also updated with more fun drops, adjustable difficulty and way faster leveling.
So, mostly what I want to say is that I'm pretty impressed of the way Blizzard has reacted to the feedback they received about the numerous flaws of the original Diablo 3 and how much change they were willing to go through to fix them.