I've thought about starting a thread like this the past couple of days, but was waiting for someone else to........
Anywho, I picked up the DVD version today for my girlfriend and I to play. I never played much of the original Sims, so I can't really give any thoughts on differences and improvements. The interface looks the same to a casual observer like me, but I'm sure things have been tweaked a bit. The graphics are pretty darn good for a game such as this, although nothing impressive or never seen before. With my main system info in my sig, I'm able to run this game at 1600x1200 4xAA/4xAF with no problems whatsoever. It's smooth as hell, and I've yet to see a frame rate drop anywhere in the game.
I did experience some frustration, though. I originally started making my own sims, a guy and a girl. After atleast 30 minutes of creating (time gets away), I was almost done with the girl when the game crashed. I got a dialog box that simply said "The Sims 2 has crashed, and will exit now", or something to that simple effect. So basically, I lost all my work. I then used the external Body Shop program to create my sims again, and actually found it to be a tad faster to navigate, although this could be because it was my second time through. When I finally got back into the game, I found that my sims I had created in the Body Shop didn't translate 100% into the game, with minor changes to the face and most all clothing (all situations).
Another thing I do not care for is the inability to scroll to the right with my dual monitor setup. When I move my cursor to the right side of the screen, it just continues out of the game and onto the second monitor. I'm optomistic that there is a fix for this, or it can be fixed in the future. Until then, I can either disable my second monitor (which sucks), or move my cursor to the extreme right of the screen without going onto the other monitor.
I'll give some more thoughts when I actually play the game a bit.