1. I never test the TouchWiz UI, but it's like iOS, it's easy.
2. You need to touch the screen, isn't hard, but isn't easy at all.
3. Look the web, i test it about a week and without any connection (only 2G) 3 days, with all the connections (GPS, WIFI, 3G) a day or less.
4. Very clean =)
5...