My beta (USA!)Spotify account didn't work at first because of an invisible space I typed after my username but after a backspace it seems to be fine with Qspace, the only client I've tried so far. I will see how this works and consider dropping my Rhapsody account.

Correction: Neither Qspot or Yaspot can actually play songs from Spotify on my N900 with the beta account I have. I seemed to log in ok, but that is as far as I got.