Wirelessly posted (Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.0) BlackBerry8700/4.1.0 Profile/MIDP-2.0 Configuration/CLDC-1.1 VendorID/100)
Cingular is deploying HSDPA; the network is live in some metro areas. Check its site for details. No BB, however, supports it.
Incidentally, Tmo will be deploying UMTS/HSDPA on its newly won 2100, whereas Cingular uses 1900, so a high-speed Tmo BB will not necessarily work on Cingular's network and vice versa.