Somehow I forgot to mention one of the key reasons why I settled on this particular phone: it works on the "world" 3G frequency (2100 Mhz), in addition to the AT&T ones (850/1900 Mhz). Sadly, not many phones support all three frequencies: for instance, the soon-to-be-released and otherwise awesome HTC Inspire 4G seemingly only supports AT&T’s frequencies. Travel outside of North America, and you get GPRS or EDGE speeds 😦
Not very many phones support both US and world frequencies; the Samsung Vibrant (the Captivate’s T-Mobile cousin) does, as do, of course, the iPhone (3, 3GS and 4) and the iPad. If anybody knows of other "world" 3G phones, please let me know by leaving a comment.