If you use star ratings in CatDV 9 they'd be lost if you exchange catalogs with someone using CatDV 8 so if you edit the ratings it will change the 'good' status, and vice versa, using the following equivalences:
Unrated = 0 stars
No good = 1 star
Maybe? = 2 stars
Good = 4 stars
This means that if you switch between versions you won't get the nuances of 3 or 5 star ratings but at least you won't lose your ratings altogether.