iPhone 3G S
Pros - Bright, high-quality fingerprint-resistant touchscreen; extremely fast and responsive; built-in GPS and compass; voice control for phone dialing and music; decent autofocus camera with SD video capability; all the new features of iPhone OS 3.0 Software Update.
Cons - Soft-looking video; Voice Control lacks some polish; onboard video trimming is destructive; requires two-year commitment to AT&T Wireless for lowest prices.
3GS
It appears, from Apple's web site, the written convention for the new iPhone has gone from 3G S to 3GS. (Although, Apple continues using the box-outline around the S when used as an icon version.)