Yesterday November 15 iTunes Match became available. I learned about it’s availability about 14:00. However when I tried to join it told me to try back later. Around 15:30 I was finally able to sign up and pay for the service, which is approximately $25.00 a year. After signing up, it asked me if I wanted to add my library to iCloud Match, I said yes but it didn’t do anything. The only songs it recognize were the ones I had purchased from iTunes. Around 7:30 I reopened iTunes and it asked me again if I wanted to add the library to iTunes Match I said yes again and this time it started the process. The first thing it did was go through and match the songs in my library that were also available in the iTunes store. That took a couple of hours to complete. Once that was done it started taking the remaining songs and adding them. When I went to bed around 23:00 it still had a couple of hundred songs to process. Everything was completed by the time I got up this morning. There were about a 100 songs that had a cloud with an exclamation point in them and the word error. I highlighted those songs and hit control and then add to iTunes Match, it added most of the rest of the songs. It also showed duplicate songs that I had in my library that it did not upload. It is not clear what iTunes considers duplicate and what part of the metadata it is looking at, so if you delete the songs from iTunes I recommend keeping the files. Once iTunes match is finished with your library, then you can then start it on your iOs devices. To do this on your iOS device go to Settings and then Music and turn on iTunes Match. Right below that is Show All Music if you leave that off it will only show the songs that you have downloaded to the device. Turn it on and you will see all the songs in your library that are available through the cloud. Beware that once you turn iTunes Match on, it will erase all the songs that are on your iOs device.
There are a couple of things that I have noticed while playing around with it. The first thing is I am missing a lot of album artwork. It does takes a couple of seconds for songs to start while they are caching. If you have more than 25,000 songs in your library that were not purchased from iTunes, iTunes Match will not work. 
There is a way around the limitation but it is a little convoluted. If you have songs that are greater than 246 Kbps ACC quality then you will want to back those up and save them elsewhere. iTunes Match will only render the 246 Kbps version. Some people are also having issues with iTunes Match not picking up the right meta data and matching the wrong song.
So far after playing with it for only a day I like iTunes Match, especially since I only have a 16 kb iPhone. I love the fact that now all my songs are available anywhere I have a connection. Playlist that are created on the iOs device will also appear in your iTunes library and vice a versa. It has freed up a lot of space for other things. What do you think of iTunes Match do you plan to use it or not.