Makes me wonder if these are new 3G users on T-Mobile's network. Switching between 3G and Edge is quite common, and entirely a function of the 3G coverage in your area, which is often spotty, but slowly improving. I see this all the time on my G1, but it happens less and less as 3G coverage improves. The issue seems to be that the towers that support 3G have a different range than the towers that support GPRS. Naturally, T-Mobile tries to do the cost-effective thing and only upgrade the towers that will give them the requisite coverage. However, that isn't always easy to predict.
Also, with newer phones, including the Nokia E72, E75, and the Motorola Milestone, there is absolutely no problem when switching over. Data connections don't drop a bit, voice isn't lagging or anything. I wonder if these people actually experience problems or whether they just sit and stare at their status bar icons.
Repeat after me: The singular of anecdotes is not data.
I believe that's "The plural..."
You are right, of course, and I should have said "The singular of anecdotes isn't data, either" - the nexus reports obviously have a bunch of anecdotal "evidence" behind them :)
Haven't had a single problem here in Austin, TX...3G is fast and haven't switched over to EDGE one time???
Zero problems with the phone so far, I'm in NYC. Spent the weekend in VT and worked fine there as well.