iTunes match has been officially released, allowing you to store up to 25,000 iTunes tracks in the cloud and stream or download instantly to iTunes or your iOS devices. The service costs $25 a year and works as advertised. I have been testing it for weeks. The only glitch I sometimes see is that the music does not always match the song title and album art listed when I shuffle all songs.
Reports are out that the servers are busy and not everyone is able to sign up right now. My advice, wait a few more days and save yourself the hassle of dealing with overloaded servers.