Well, maybe this is the wrong place to post this, since I've only seen negative opinions, but I got the game and have been having a blast with it.
Speed-wise it's really optimized - compared to Sims 2 which chugged hard-disk. They've abstracted a few things - for instance, your Sims no longer take 45 minutes to open a car door and sit in the car, instead they sort of "morph" into cars or bicycles or Taxis when they touch the road. I actually welcome the change. Also town buildings aren't there to be explored, they provide a function: some lots have sort of "prefabs" that are huge buildings that you just click on and use - such as a shop, or a workplace. Others are filled with items to interact with, such as the gym, art gallery, public pools, parks, etc.
There is a lot of things to do. I played nearly all weekend with a small family and it was almost too easy, so I started over and created a 8 member family (4 young adults and 4 teens) and spent most of my Sunday juggling jobs and micromanaging them and has been fun.
Also: you no longer have a general play area and choose to play different families. You start a new game, using (in this version at least) the only City map available for now. Each saved game creates a copy of the whole thing. You're playing one family specifically - trying to juggle families is not a viable option, since your current one gets abandoned "permanently" if you choose a new one, meaning that when or if you decide to play them again, all their wishes will be reset, and other changes would have happened to them (aging, lost of jobs, death, etc). So, effectively your family is the PCs and everybody else are NPCs (unless you marry and they move in). Also, NPCs keep getting more and more children and dying of old age and so on.
I think it's fun and it's far more simulational than the earlier versions.