Destructoid was able to demo The Sims 3 and they bring their thoughts as well as information to the table.

I was given a demo of The Sims 3 by Grant Rodiek, an Associate Producer on the game. He told me that while The Sims 2 was certainly a great game, the main problem with it was that the Sims themselves were too needy. They needed constant monitoring, or they’d soil themselves — the game became more about keeping the Sims alive, as opposed to watching them live their lives. So the aim with The Sims 3 was to move up Maslow’s hierarchy — to “move past peeing,” as Grant put it.

To that end, two of the previous game’s eight needs have been excised; comfort and environment have been replaced by “moodlets,” which are special events that will have a temporary effect on the Sims’ behavior. You can allow the world to just take care of itself — Sims will eat and excrete on their own. Instead of needs, The Sims 3 focuses on two major areas: personality and customization. Five “traits” will determine the personality of a particular Sim (toddlers: 2, children: 3, teens: 4, young adults: 5), and there are over eighty of them to choose from. Some of them are pretty standard (Charismatic, Vegetarian), but many of them are whimsical and make for fun (often comical) game scenarios.

Read the huge preview here