To expand my first comment from above:
I've now listened to both the full FRAGILE soundtrack and the MintJam album. The FRAGILE album ended up straight in my wishlist. That shows again how subjective a music review is
Like stated before I'm very fond of ambience and piano and therefore this album really does it for me.
I'm not yet convinced about the MintJam album. I haven't listened to many works from MintJam yet, but like you guys already say - the vocalist (TERRA if I did understand you correctly) is doing a pretty good job. Key's music is pretty new to me as well (I have only watched Kanon and Clannad, still have to take a look at AIR - never came in contact with Little Busters!).
The track "Last Regrets" is exceptionally good IMHO. That one should be the cover of the Kanon intro theme if memory serves me right. I already liked the original version, but the cover is even better. Well, maybe not really "better" but good in it's own way.
I hoped for a cover version of the opening theme of Clannad After Story, but didn't find anything (I can't assign all Clannad songs, maybe these are exclusive to the game?).
Alicemagic is the next track that stands out. Would be interesting to hear the source material - does someone have a clue which track they're covering here?