Quick drive by...
The atmosphere and music holds true to the Diablo standard, I love it and sometimes get that creepy feeling with the scenes and music come together.
The scenes and battle grounds have a great sense of depth and perspective to them. You feel like you are on a bridge over a chasm.
Barbarian makes great Hulk, smash character. I have had great success with using my ground stomp stun power and whacking away until unstunned, dancing around and stunning again etc. for the BBGs, and adding runes for effectiveness to my cleave and wading through armies of minions.
Act I is great, flavorful, etc., but even on Normal setting the difficulty ramps up in Act II. Don't play mindless click click in Act II. (some say you can "faceroll" the entire game on Normal, but I don't agree, I found some tricky spots I had to use tactics and switch powers.)
Monk has a lot of flavor and class, only level 4. Wizard is great for ranged, but in trouble if you get swarmed at low levels.
My Barb and a friend's wizard @level 15 made a great combo. When my stun wore off, he would freeze it. But the play was such that timing was important, it was not an easy setup and not an I win button...but the tactics helped.
I wanted a separate banner for each character, sadly the design is per account.
I don't like mandatory internet connection for a single player game, but other than day one, it has not affected me. And having a friend "jump" in was cool.
We killed an end boss together, but later when I went back to solo mode, I still had to kill that mob to progress, parts of this are confusing to me so be careful what games you join/leave with your main solo person.
Finally, the way the heads roll and bounce down the hall when you whack the basket of sacrificial heads is too cool/freaky!