I agree with The Oolong Man's implications of Musicmatch Jukebox's problem. It is too tyrannical. It does too much automatically, without asking. If you use TweakUI to disable cd-autoplay, then tough. Every time MMJB starts it turns it back on. In Win9X I disabled auto-insert at the hardware level, but in Win2k I can't find that, and it's just plain obnoxious no matter what.
In the latest version of MMJB I too can not get it to stop bugging me about claiming file formats.
It is buggy. It just now(last version I think) started having real playlist use - a couple versions ago I wanted to open a playlist I created in Winamp and burn it to a cd--Musicmatch would only let me open playlists created in musicmatch, or residing in my "My Music" folder(which I don't use).
I personally find Musicmatch to be extremely slow and kludgy, despite running it on 600mhz machines with 128mb RAM. It has flashy and useless stuff that you can't get rid of. I often hit "hidden" links in the interface, which go slowly launching a web browser when I was just trying to drag the player over a few pixels.
Musicmatch isn't free(its disabled shareware). Winamp and CDex(and other ripping utilities) are completely free, and IMO faster, more stable, and just plain better.

Regardless, I've used Musicmatch Jukebox a whole lot for ripping cds, and would probably have paid for the full version if not for the problems listed above.