I just confirmed with multiple AT&T customer service reps as well as another SGS2 owner that you have to be on a 4G plan in order to get HSPA+ speeds with a device on their network. That means if you switched from a 3G device to the SGS2 without switching your plan, you are still only using your device on the 3G network. To make things more complicated, the SGS2 does not have a recognized IMEI in AT&T's system so the reps don't have the ability to move you to a 4G plan. One workaround is to use a friend's IMEI from a 4G device to put in AT&T's billing system (it won't affect your friend's service) but this is more than a pain in the a$$. I don't know of another workaround and wanted to know if anyone else has one before I get my device tomorrow. Thanks.