I know there are several biorb (and related product) forums around the tinterweb - most of who advocate modifications (bare minimum being upgrade of the airpump etc) so these would be worth checking out.
I like the idea of biorbs - just not the massively over inflated prices for the media etc (which im sure dont need changing every month etc) and i do admit they can look rather smart (I like the acrylic stand and the ltd ed blue tint biorb) - If I ever decide to try bettas again - I may go for a biorb but 'modify' it - ALOT