Not bad, but in many ways a setback to Sims 2
However, when you are used to the complexity of Sims 2, Sims 3 is just a letdown. So many items and things you could do are just gone. I really miss those cinematics of first time events, like First Kiss or the Wedding. It looks all so mundane now.
And who the heck made all those round hobbit faces? Or those abysmally bad and few male haircuts? Some stuff is really terrible. And EA is ripping off people, when you check out how expensive just a few downloadable items and set are.
But the worst, hardly mentioned is: when you change to another Family, ALL the other families you created live on with their lives, single people may get babies out of nothing, or some Sims even may move entirely away. I already lost 2 single sims I had created and "parked", who moved away and were gone. The check options don't change that, so you focus on one family or you are doomed.
Also so many small animations are just gone. Where once Sims went into a car, drove out to the street, now they teleport the car on the street and the sim into the car. No animation whatsoever. Some SIms are dumb are pie, and stand around endlessly for no reason.
To me it feels like a "Sims light" version. I am greatly disappointed, tho it is solid for those who never played Sims 2 to compare.