According to some Japanese reviews, the remastering seems to be done carefully and truthfully reflects the original Melodya sound. Comparision shows that Yedang versions are slightly better than the ones on Revelation when the same sources are involved.
You can listen to the first 2 minutes of every track on all 90 CDs here.
http://www.lalalamusic.net/yedang_list/
allcdlist_01.html