MPFreaker works by analyzing your music library and using Internet databases to properly re-tag your tracks. For iTunes 4 fans, its most obvious strength is that you can use it to find and add album artwork to all your music. But if you're like me, you've probably got some tracks that need more than just artwork.
I've still got a lot of music I ripped from CDs a long time ago. Yes, I'm slowly going through my library and re-ripping all my tracks as high-quality variable bit rate MP3s. But it's a slow process, and I've still got old tracks I ripped using AudioCatalyst and SoundJam back in the day. To my chagrin, I found that I had numerous albums that didn't even have proper track information. Pathetic. But I pointed MPFreaker at those albums and, blammo, not only did I have proper track numbers, but the album's year information and cover art as well.
Good stuff -- probably worth the $20 price tag right there. However, as you might expect, I do have a bunch of feature requests for the next version. MPFreaker is nice, but it doesn't quite match up with the features I've seen in PC programs such as Musicmatch Jukebox. Musicmatch is a lousy jukebox, but its Super Tagging feature -- which is very smart about ferreting out possible matches to your tracks -- is impressive. MusicMatch also prompts you to confirm song matches (from multiple possibilities), something that MPFreaker doesn't do.
Still, MPFreaker's got features I haven't seen on the Mac before, and it has done a wonderful job of straightening up my MP3 collection. If only I could press a button and straighten up my office as easily.