Not totally unexpected, and not as revolutionary as some were hoping. Honestly, I was keeping my expectations low because I wasn't overly expecting anything ground breaking out of this announcement.
Alex says "we don?t think anyone will be disappointed with the display tech Samsung?s brought to bear on the S III.", but while I obviously haven't seen the screen, I'm a bit disappointed that we didn't see SAMOLED HD PLUS in this screen. While I think the screen on the Galaxy Nexus does look nice (and according to Alex this screen might look a tad better), my eyes are pretty sensitive to the Pentile matrix, and it would bug me after awhile. The screen alone will probably be the sole factor from keeping me from upgrading from the GSII early, depending on how the US variants turn out.
Other thoughts ...
I bet the single button is not included in the US variants. Maybe a 3 capacitive button layout like the One X.
I'm a fan of expandable storage and a removable battery, and I'm glad they stuck with it. However, I agree with Kevin to an extent. I'd be perfectly happy with 32 to 64 GB non-removable internal memory. I do hope Android manufacturers get there eventually.
The design looks sleek and nice to the eye, but nothing drastic over the GSII. More subtle and refined in comparison I'd say.
Final thoughts ...
This will be a successful device, but I don't see it being a big pull on existing GSII owners. Depending on how the individual US carrier variants play out, I will probably be sticking with my Epic 4G Touch into 2013.