I had the H&V fantasmic package booked for this past June, but went ahead and cancelled it (and Tony's Town Square) for Cali. Grill. IMO, it was worth it to me. We still went to Fantasmic, and had MUCH better seats than we would have had, had we done the package. Grant it, we waited in line for a little longer, but haveing the better seats and be able to pick a restaurant that was more suited for us was worth cancelling it.
(just a side note... when planning ADR's at MGM.... I ALWAYS have a hard time picking something. It seems like there are much better options elsewhere to me.)