Well, okay, craptastic means 'crappily good', but that could still mean a couple of things:
1) It's not as crap as 'crap', possibly in a slightly perplexing, kitsch way. It's able to bend the conventions of whatever it is it's doing so shamelessly it's not at clear what it's attempting. Ergo, it's impossible to reach a precise judgement on it.
2) It's crappier than 'crap', but eminently watchable in the same way that car accidents, bomb explosions and Dogz' posts could somehow draw people to bear witness to them.
And y'know, various grey areas and shades in between.
Sweetness, sweetness, I was only joking when I said I'd like to smash every tooth in your head . . .