Carriers seem more bothered about loosing customers than manufacturers do. If they had even 100 people on their forums complaining and saying "I'm never getting a phone with t-mobile" again then not only are they loosing 100 customers others will read the posts and might well stay away. That's the kind of publicity they don't want. So yeah, it might make them push Samsung or if nothing else offer their customers a different phone (I know i'd be happy to get a newer Android phone and put this Samsung nightmare behind me if my provider offered me one).
Indeed I just emailed o2 asking for that. My main grump was the bugs (yesterday I had the dialpad bug meaning I couldn't get through to the department I wanted) and said that was the last of a long list of bugs with this phone and I want to exchange it. I didn't even mention Froyo, etc it's not like they promised that, but bugs are another matter. I'm not too hopeful but worth a shot.