I've played Sims 3 for about 12 hours now. The first 8 hours I was really hooked, its similar to Sims 1 but definitely better. There is less micro to keep your mood bars constantly filled (good), but its still there as it should be. In this time I got my sim to 10/10 career rank as a thief, and then a few promotions after that up to making ~700/hr. I got the best of most appliances, built a nice pool/backyard, got my lifetime achievement award (maxed logic and athletics) and bought the best awards imo, which make it so I rarely have to eat, use bathroom, or use the shower. Things were a lot of fun, but then I found myself with not a lot to do. Basically I can marry a woman and pump out kids and do it over again, or continue making lots of cash and building/designing my house or saving for the 100 000 car. I must admit I've lost most of my interest at this point, rather suddenly. I think some people, especially women, will get a lot more out of this though - I knew a girl who mainly played The Sims for the designing aspect, she became an interior designer.
For anyone who wants gameplay tips: I recommend getting a computer asap and "playing computer games" to raise fun to the max as often as possible. Doing this nets you +40 mood for 8 hours, which is huge, and the computer is the best way to do this until you can afford the 2 most expensive tvs. You can also gain social and fun by "chatting with someone." Social is actually pretty easy to keep filled with using the cellphone though, I remember it being much more difficult in Sims 1. While your mood is nearly maxed out you accumulate the achievement points which get you really useful upgrades, and keeping fun maxed out makes it relatively easy to keep that going 90% of the time.