Canon lens on Nikon body?

I own a Canon body with a Canon efs 15-85 lens. I'm in the market for a new body (cropped sensor) and am looking at the D7000 or the D300s (and also Canon's 7D). I'm wondering if there's issues using competitor lenses on Nikon body?

Also, I'm wondering about overall image quality. I've seen some amazing photos (clear and sharp) from both makers but it appears Nikon has the edge. I'm coming over to this side of the forum to ask that question. I enjoy shooting airplanes and recently rented a 100-400L with my XTi and was imrpessed but I still wasn't achieving clarity I've seen on popular sites like airliners.net. What will it take to get extreme image quality?