It sucks.
it's for free on Wii and PS3.
Just bought a wireless network adaptor (why???) and 3 months subscription. Got the message "gamertag occupied" when connecting to Live. Got to change the name of the gamertag, which I did. But a completely new gamertag was created and tied to the Live-account (with 0 achievements).
Impossible to change and not possible to get the money back.