I have a Samsung Galaxy S and I need to get hold of a SIM which will give me 3G (or GPRS) data access in the US.
The Galaxy S supports quad band 2G (850 / 900 / 1800 / 1900) and tri band 3G (900 / 1900 / 2100).
This limits you to GPRS/EDGE on T-mobile USA or GPRS/EDGE and 3G on AT&T. (The US T-mobile uses 1700 for their 3G, a unique to them frequency).
EDGE is the enhanced GPRS upto theoretically about 200kbps, whereas GPRS is 50kbps.
Don't forget the handset needs to be unlocked.
pro - on THFB - sync about 17.2mbps - BQM