One of the things I love about encoding my music into the ogg vorbis format is the use of custom tags, especially for my classical CDs. For example, this file of a movement from Mahler’s 6th symphony has tags labeling the Label of the CD, conductor, and symphony.
I just wish there were a way for Winamp, or any other player, to be able to search custom vorbis tags for things such as conductor, orchestra, or any other tag I use frequently such as violinist, pianist, etc. If I had such a program/feature, it would be easy to sort or search for all the recordings featuring the New York Philharmonic, or any pieces played by Martha Argerich for example. I guess that can be one of the disadvantages of using a less well known or used format. But at least there’s an excellent portable music player that supports ogg vorbis.