So here are my first impressions on the game:
1. It's pretty. Not as pretty as it looked like in the youtube videos and stuff I watched, but it's still MUCH better than D2.
2. It seems a little fast... I noticed that just with me and another guy we seemed to fly through all of the quests. I'm not sure how far the different acts go, but it just felt like we were going to be done with act 1 in about 45 minutes.
3. Demon Hunter (the class I played as until I had to come back to work) is quite weak compared to the other classes it seems. I was with a witch doctor, and his little spiders were tearing it up MUCH faster than I could with a crossbow.
4. The town you start in isn't quite as intuitive as Act 1 on Diablo 2 (Rogue Encampment, I believe?) It's very linear, and was somewhat weird for me to navigate at first.
Overall in the 45 minutes or so I played, I enjoyed it. There are some things that were different than I expected, but that's how every game is.