Yes, you can park hop among the 4 theme parks...but if you want to go to the water parks or Disney Quest at DTD you either need to pay for your admission as you go or buy the Premium AP's. (At the present time I think DVC members get about $4 off the full price admissions for those.)
Another question...
if you use your Disney visa...
does this qualify for 6 months interest free?
When you multiple them out for a family... it gets up there!