This is a step-up from the previous Sims games in that you can customise so much more. The game is smooth and you can focus on one family or create more to customise your whole world. There's much more interaction between sims too.
My only complaint would be that the sims are a bit more autonomous – for example, if you create more than one family, the first family will continue to age, etc. While you're playing the second. It came as a surprise to me when I went back to the first family that they'd aged beyond child-bearing so I had to adopt kids in order to carry on the family name.
Other than that, I enjoy this game, especially with the add-on expansions.