Just re-flashed my backup (rooted FRG22D plain vanilla) after a few days with CM6.1RC2.
The CM6.1 worked fine for the most part but I did experience a few minor glitches that I don't have time to deal with on a daily basis.
1/ Keyboard... I use a custom themed HTC IME keyboard and the ROM kept changing keyboards on me switching back to the stock Android keyboard several times a day.
2/ Wallpapers... I was using a live wallpaper (Snowfall free) and the Rom would occasionally switch back to the stock grass wallpaper.
3/ Widgets... Constant "problem loading widget" messages requiring trashing the placeholder and re-loading the widget to the screen. Plus not all widgets are available for all the applications that have them.
4/ Music Player... I tried several music players (stock, AMP, and Cubed3) and none of them could read the files on my SD card and kept telling me there were "No files in the playlist"
All in all not bad and I did learn to like ROM Manager because it lets me do other things while it is backing up, wiping and flashing so it does free up some time for me.
Can't wait for the final version on this!