For complete albums, I use My Documents\My Music\Complete Albums\Artist\Album\Artist - Title
For singles, I just use My Documents\My Music\Singles\ followed by a letter of the alphabet that corresponds to the first letter of the Artist (not counting "The").
I really don't care about genre that much when it comes to music, and I only use MJ to play, and it keeps track of all the track numbers and all that. I never really understood why I would need all of the tag information as part of the filename when I use a jukebox app that keeps track of all that for me.
I mean, when it comes right down to it, you could just throw every song into one giant directory (barring any filesystem limitations) and give them all just a bunch of gibberish for names, and you could still see a nice a neatly organized music collection within MJ.
It's all about the tags, baby. Filenames were really only important way back in the early days of Winamp 2 and Sonique, and even they would read some tag info.