I have. It took absolutely ages to scan through the music, match it, and upload the ones it didn't recognise (about 1000 songs), but once it had done that it works brilliantly.
I'll just use it for a year I think - I did it really to save re-ripping loads of CDs that I ripped ages ago at low bit rate - it's less tedious to up the bit rate via match, though it would be easier with an applescript, I guess.
Does it work with Audiobooks (or files classified as Audiobooks), Blandy?
Dem, basically iTunes match scans your iTunes library for songs that you currently have on your hard drive. It then looks in the iTunes catalogue for those songs and "allocates" them to you in the cloud, at the higher Apple standard bitrate.
The amazing thing about it is that it also scans in the dodgy pirated MP3's that you've downloaded via illegal means, and then lets you "own" them legally.
To me, it's the record labels final acceptance that they are never going to fully stop illegal music downloads. By using iTunes match, iTunes will pay the labels a royalty for songs that it stores in the cloud. By a very roundabout way, the labels are getting some cash for that Eminem CD you downloaded via a Torrent site back in 2009.