It's pretty good, though very standard fare. But that's OK as I like that. I'd rather have a good game without gimmicks than something that tries something new and fails. The prices in the shops seem pretty high, though. Also I can only play for about 20 minutes at a time as this game is EXTREMELY stressful on the CD-ROM mechanics. Everything loads. It's like a CD System 2.0 game with only 64k of memory, very similar to Cosmic Fantasy 2 in the amount of loads. It needs to load every battle, every town, everything. And it does this A LOT. I am actually surprised that Super CD is required. But as a result my CD drive will eventually "forget" to load until I nudge it. After a few times of that, I just turn it off. After it has cooled down it is fine again. This happens occasionally on other games, too. Always has since day one. But Mysterious Song really brings this issue out like no other game.
EDIT: I think incorporating PSG music would have been much less stressful on the system.