So, I have the demo. I played around with it yesterday and here are my first thoughts.
I actually liked the interface and found it very simple to use - just click on the bit of sim you are interested in and a load of options appear.
You can choose male/female (of course) and weight and "fitness". Those are sliders - then the "fiddly" bit come in.
I found that you have to choose the archetype and adjust that - the archetypes are pretty good, but its hard to find all the options. I think there will be chat threads on "hey I found slider x" appearing for years to come as the game help is laughable. I think if you are the type who read the instructions then you are looking for a comprehensive overview. There isn't one.
Hair and eye color options are horrible. Lets hope this is just a subset of the full game options.
Incredibly arg, not tactile at all. I want my sliders back I really miss the option to blend face type A with B (from TS2 Bodyshop) as I think sims are gonna look pretty samey.
Lots of nice guys clothes, there being no CASt and no CC as yet makes it feel really hard to give your sim a decent look.