A good cover and title have to pull in the reader—they have to give away a bit about the story. My titles are all short and to the point and the reader will always have an "aha" moment when reading my books. While my titles may sound obscure, they are relevant.
As a reader, a good cover will make me pick up the book, but strong back cover content will push me to buy it. I don't want to see the back smattered with quotes. I want a quick synopsis. That's what sells it to me.
All in all, if the cover design is shoddy, selling to me is nearly impossible. I'm a marketer by trade, and I do judge a book by its cover.