Reading their comments on the breakup, it sounds like they want to leave behind the "idol" life and try new things. (Relationships with the opposite sex, maybe?) By that definition, Ongaku Gatas seems almost like a step backward for them. Of course, that's the standard message for all of these types of dissolutions, so there's always the chance that it's all BS.
I did like it though when she was in the Gatas Hawaii fanclub tour and was performing on stage with the other girls who are in Ongaku Gatas.