Lies, damned lies, and statistics
I'd be interested to know EXACTLY how the question was phrased indicating people were "very satisfied" with AT&T's service. People I've talked to generally say *AT&T*'s service sucks, but they are overall satisfied anyway because they love the IPhone so much. Keep in mind, Verizon & Sprint, a lot of the local carriers, Cricket, and MetroPCS are CDMA, so if you want a GSM phone but not AT&T the choice is like T-Mobile or another local GSM carrier, if there are any. And T-Mobile runs 3G at 1700mhz, so the IPhone will run EDGE-only with them.
Secondly, this problem wouldn't ONLY affect the HSUPA phones. This is a shared channel, so unless the channel is pretty clear, an HSUPA uplink running less efficiently than it could be is taking away capacity that could be allocated to other users, HSUPA or not.