And here comes the same old fight about the importance of the covers
To me, in the end the music is definitely most important. However, the covers are supposed to reflect the feeling of the music in 1 glance, it's what people see when they browse CD's in the stores, and it's the image they have in their head when they think about the single.
That's why, in my opinion, a good cover is
very important. A bad one wouldn't ruin the single for me, but a good one will definitely boost my anticipation level a lot.