I actually don't think that's an ugly album cover at all. It's a hell of a lot more attractive than other STP artwork like this:
Anyway, to your original question I have to say I do have kind of a hard time buying albums that have ugly covers. Part of it I'm sure is that design is what I do professionally so I'm sensitive to it. But also there does seem to be some kind of rule that if the artwork sucks there's a very good chance the music sucks.