I have had success with my Robert Johnson video (which isn't a cover, but rather a music video of the actual song. But the idea is the same). But I have clients who have had both success and difficulty with the strategy. They key is making sure the content lines up with the expectation of the visitor. If you are a banjo player doing a cover of a hip hop song, those searching for the hip hop song might not be interested in your cover, if you get what I'm saying. So take that congruencey into consideration before selecting a cover and that might help. Another thing to remember is that your call to action needs to be fairly bold. YouTube can be a difficult vehicle for click throughs. The plus is that it can also be a source of a lot of easy traffic.