Thanks for the answers. Two quick follow-ups:
1. I know lots of programs will look up the info for you -- the advantage of MM (to me anyway), is that it will update the tags automatically at the same time. This is handy when you're looking up the tags for 10 or so disparate songs at once. The last thing I want to do is look up the info in a database and then manually enter the tag info for each of the files, one at a time. Make sense? I'm asking if MC not only looks up the info, but (once you confirm it) tags the info to the song in the same step.
2. Re: psychic mp3 -- my impression, though I've never used it, is that it works only for mp3s. I have a lot of ogg files too. I sometimes use this program:
http://www.mp3tag.de/en/index.html and it works quite well. However, the primary reason for me to switch to MC would be the all-in-one aspect of it. (Oh, and the Tivo interoperability is a big selling point too.) Right now I have about five separate programs I use for various things. But most of them are free, and $40 is pretty steep, especially for me, right now, knowing that I'd have to pay more when v10 (v11, v12, etc.) comes out.