The Sims Resource posted an article with lots of information about The Sims 3. It looks... pretty impressive, but I remain skeptical.
You can read the article here.
Some highlights:
5) Young adult is the new default age and is changed to represent life between 18 and 30 years.
6) Adult now considered more 'middle age' and includes wrinkles.
27) New timeline dragbar which is specific to a few interactions. This lets you control how long a Sim spends on certain tasks like sleeping, fishing etc…
34) Brush teeth is back - Gives a "minty breath" moodlet.
40) Hair includes 4 layers: Roots, Base, Tips, Highlights. You can choose any color to apply to these 4 layers and can be saved as a preset.
41) Eye color by any RGB (freeform color pallet) and can also be saved as a preset.
45) Change voice and even pitch so thousands of unique vocal sounds. You will be able to recognise by sound which Sim is talking!
52) Young Adult and up have 5 traits, Teen have 4 traits, Kids have 3 traits, Toddler has 2 traits.
62) Free placement of objects allows you to put things exactly where you want them.
70) Multiple decorative items on 1 surface (as long as they don't overlap).
75) Can move the house to a bigger Lot (upgrade as funds allow)