Mark has a ton of mp3s and he wants to put accurate ID3 tags on them. He's used iTunes Match for his songs which adds the ID3 tags, but they aren't accurate. Leo says that Media Monkey is better than iTunes Match and it's far more accurate. It'll give album art in addition to ID3 tags. The tag editor is easy to use and he can do it by batch as well.
Amazon also just announced an iTunes Match like service for Amazon Cloud Player. It's $25, and will convert songs to 256kb mp3 with tagging.