Jay Tuley's original IEatBrainz apparently went defunct before it ever grew up to be a Universal build. Fortunately for us, Pierre Andrews picked up the (open) source code and made a version that works for just about everybody.
IEatBrainz uses the online acoustic fingerprint service "MusicBrainz" to fix improperly tagged files in your iTunes collection. It's simple, easy and pretty fast considering the number of web transactions it has to make. It serves as a great interface to MusicBrainz, which has to take the blame for any inaccuracies. The software allows you to select files from your library to check, and begins looking them up in the background while you're still picking files. You get a chance to review the ones that it thinks it found matches for before sending the information to iTunes.
For various and sundry reasons I have a lot of poorly tagged files in iTunes, so I spent some time seeing what it could fix. I have to tell you, it handled Black Metal and Classical quite well, scoring almost 100%. Other genres baffled MusicBrainz a little. My Dead Boys tracks were a wash and it told me that Siouxsie was actually Switchblade Symphony. Overall, about 60%, but I have some very obscure tracks. I don't even know what some of them are.
It's free, and no one will question why you have so many untagged tracks. We promise. You can grab the Universal build at 6V8.
Update from the developer's website: "Jay Tuley just contacted me to explain why a universal build had never been released. Basically, the TRM fingerprinting system provided by MusicBrainz will be switched off in the upcoming weeks/days. After that, even if you can run IEatBrainz, it won't find any result as the MusicBrainz servers won't be answering the requests."