You would see the "3.5" under the signal-strength bars (when transfering data) instead of "3G" (UMTS, used either in a non-HSDPA cell, or when data is not being transferred) or "2.5" (meaning EDGE (which of course is technically 3G, despite being a bitrate enhancement of GPRS, but is usually referred to as 2.75G, 2.9G, or similar, reserving "3G" for UMTS) and I believe would also show for plain GPRS, although I'm uncertain there). I'm a little unclear as to why one would want to disable HSDPA, could someone explain?