This all brings up an interesting point. The iPhone has been around for about 3 years now (I think) and it still can up date it's oldest phone. Pre has been around for a year and the updates still work. Android has been around for a year and it already has software that cannot update to their latest OS.
It kind of shows to me that Android's OS is developing significantly faster then the other OS's. I mean, even aesthetically, the OS from version 1 is completely different to version 2. Opposed to the iPhone where the OS looks the same even going into it's 4th version.
This is pretty much my only big concern about Android phones. I like to keep up to date, especially when it comes to operating systems on my devices. (The only exception being I skipped Vista on my PC, which up until I got my iPod Touch at Christmas was the only device I really had to worry about. It was almost as difficult skipping as I imagine the problems in Vista would have been had I updated. But I got Windows 7 day 1.. heck, day -100 or something, actually, as I got the RC shortly after it released.)
Anyway, rambling aside, I'm a little worried about the update paths on Android phones. That's one reason I'm hoping with Nexus One, they'll let people update as new software comes out, until the software no longer supports the hardware.
Now that I have the Nexus I am finding some apps that do not work on 2.1 but so not state any issues in the comments. For example DXTop has some issues with 2.1 but nowhere does it state that it does not support 2.1