Never had any problems with my export code. Just went into the Get More Music / Enter Code menus in RB3, entered my code and ...
Well, it gave me an error.
Had to try again a few times due to the fact the servers were way too busy. But it did eventually "export".
The keyboard is fun. I just started playing through on Pro Medium. Takes a bit to get used to Pro setup, but it's more interesting than I expected. Not all songs support keys though, and some of the ones that do don't support them well (Beautiful People for example)
My RB2 guitar is flaking out though. Boo.