Someone asked for some elaborations on the new features, so I'd thought I'd answer that. So sorry for being longwinded.
New features for the better in my opinion includes: the personality traits, which makes your sims more believable and personlike.
The neighborhood, which means that you can go anywhere in the neighbourhood (in your car/bicycle/on foot/taxi) and visit shops, neighbors and so on (no loading screens like in the previous sims, thank god!). Your friends and neighbors have lives on their own based on those personality traits and they basically manage themselves, get jobs, friends, age and so on. I find this really cool because the town lives by itself and seems very organic and alive.
The style editor in the build/buy menus give you a lot more freedom when it comes to designing. And objects now rotate 45 degrees! Awesome!
They've gotten rid of the option to build you own neighborhood from scratch, which I find a shame because I really liked that feature in the 2nd one.
I think overall it hasn't changed much graphically, although the new camera is cool and you can really view things from the sims angle and look over scenery which is very nice indeed. There are a lot of familiar things in the new sims. But they've definately improved the game, however I still find the time to be a HUGE issue, I mean I'm sitting like a monkey on a rock when they go to sleep or to work, waiting for them to wake up or come home. I really wished Maxis had added an option to make time go even faster than those 4 options.
But overall better than sims 2, not mindblowingly better in my opinion, but better. Sorry for the long post.