Very similar problem at the time, actually; UMTS chipsets had terrible battery life, to the point where Nokia actually made some of its Symbian devices in otherwise identical GPRS and UMTS versions.
Plenty of iPhone customers also give 3G by using the device on T-Mobile. There aren't that many of them though compared to the number of people who switched to AT&T (or Verizon) just as there weren't that many people who bought the iPhone 1.
I am one of them. I've got my phone jail broken and on T-Mobile's network so that I don't have to deal with AT&T (unfortunately that is going away).
The EDGE speeds are not half bad actually, when browsing on the iPhone itself they are a tad slow, but over bluetooth to my iPad for example I notice it slightly, but it doesn't really bother me.
iPhone 1 sold pretty phenomenally considering it was a $600 phone, lacked 3G, etc. T-Mobile numbers are going to be dramatically depressed by having to buy unsubsidized and break the carrier lock.