First of all, it only matched about 600 of my 2500 songs. Some of those matches we're to the wrong version of a song. I was excited for all my music to get upgraded to a higher quality, but it barely matched any tracks that I hadn't already bought on iTunes.
Third, there's no more controlling what and what does not get synced to your iPhone. I have lots of music sitting on my computer that I don't want on my iPhone. With iTunes match you're forced to see every song on your phone.
Long story short after seeing what it was like I immediately turned it off. I prefer having control over my library, iTunes Match basically turns it all over to Apple.
The matching has gotten a lot better - when I did it two weeks ago, it recognized maybe 3000/4000 songs - and I understand it's even better now.
Just use playlists - I have a smart playlist for my favorite songs that I used to sync to my iPhone but now I just leave it in the cloud.