SHN is one of the lossless formats that have been discussed around here in the past. It's mostly popular amongst people who trade live shows (bootlegs). I was originally perplexed as to why this lossless format was chosen when we all know that taped shows are generally low quality to start with, so the "loss" from even 128 kbit MP3 is simply not noticable.. However, I don't think SHN's suffer from the "frame boundary skip" problems we all know about in our quests to get gapless output. For live shows this would obviously be very important. So I can see why it became popular (though many better lossless formats with better compression have come on the scene.)

I'm pretty sure it's the most established of the lossless formats, though not the most technically advanced. SHN files are, if memory serves me correct, between 20 and 30 megs for an average length song, I can't remember the exact ratio.. But they're smaller than WAV, bigger than MP3.