I wouldn't worry about it. It's not supported offically because the Slingbox Classic has been long discontinued. That just means they're not going to develop any part of the software specifically compatible for the Classic.
There's lots of people here that got Slingplayer clients to work with the Slingbox Classic that isn't offically supported. For example, the Slingplayer Mobile for iPhone and Andriod. It's just one of those things where if the software works, great! Otherwise, sorry, its not offically supported.
I am slightly tempted to go back anyway as I think I prefered the interface on the old version. It had all controls in one panel, allowed manual orientation either vertical or horizontal, had separate volume control.
The new interface requires more clicks to do most things. The advantage is that it can be operated without a stylus and setting up favorites is easier. AND I don't get that annoying "An upgrade is available" message.
Sorry to the developers. Maybe somebody out there likes the new inteface better.
The only reason you would what to use SPM 2.0 is to view Slingbox's HD version boxes using component cables to enable wide screen on new phones.
SPM 1.6 is by far, better in picture quality and interface. I tried SPM 2.0 for about a month and switch back to 1.6, full screen on my HTC TP2 was not worth the loss of picture quality. I'll deal with the two black bars on the sides.
The update screen only appears if you reboot your device.