Welcome to the forums Myrlin.
Unfortunately, the problem you describe is nothing new. The backflip should be getting
an upgrade to Android 2.1 in Q3 2010. Technically, that could be tomorrow, or today even. The update process starts with Google releasing the Android 2.1 code, then Motorola takes it, tests it, and makes it work on their phones. Then AT&T takes it, and makes sure it works on their network and what-not, testing it as well. What's more, NO ONE should have to pay for an Android OS upgrade, so AT&T's promise that it will be free of charge is true, but if they actually did charge for it, that would be absolutely ridiculous.
As far as I know, Android 2.1 for the Backflip has not yet been released, so you are not being excluded specifically. It is definitely bad business practice by AT&T to continually tell you the update will come out in a couple days time, and then not push it out, but the phone companies like to use qualifiers like "soon" and "in a few days" and "shortly" which can mean most anything they want it to. When did you call them and get these responses from them?
Unfortunately, just because other Android phone on AT&T have Android 2.1, doesn't necessarily mean that yours is ready for Android 2.1 as well. Each phone is different, and needs a slightly different approach to get the OS upgrade working correctly, so you are just going to have to tough it out until it gets released...
There is one last hope, if there is an Android 2.1 ROM, and a process to root your Android phone. Rooting is a process that basically allows you to do almost anything possible (super-user abilities). An Android 2.1 ROM for your phone would basically be a different phone's Android 2.1 OS software, but changed by third-party programmers to work on your phone. This whole operation requires a deep understanding of your phone, and a willingness to accept that if you mess up while rooting, the phone may become permanently broken, or "bricked."
— modified on Jul 22, 2010, 4:21:45 PM