It's a great game, don't get me wrong... but some people may not like the change.
You can explore around your neighborhood, and meet tons of people. The game's AI can fail at sometimes, such as your sims walking the LONG way to certain areas. Which can be very annoying, and if you have a large family, its hard to take care of them when they're running around the city. There is still a few glitches but they will be fixed... You may need a pretty beefy computer to run it smoothly, my Intel Core Duo and 2GB of ram with Nvidia GeForce 9500 GT can't run the whole thing on full settings or else the framerate will drop and lag often.
I suggest you watch some gameplay videos and read some other reviews if this game is really for you.
Overall, excellent game 8/10.