Yep I got my email last night so I logged into the iplayer went to download something and it told me I had to use internet exploder not firefox, so I shut down FF and opened IE tried to log in and all I now get is the error message that either cookies are not enabled or another computer is using your account details. Go back to firefox it logs in with no problems.
The other thing I'm slightly concerned about is that it's P2P and the sharing software is on all the time so if you have more than one computer on line through the same router it will slow things down, it means a bit of work to stop auto loading of software at startup. which is in fact against the user agreement.