If you are going to stick a Leica M-mount lens on a Nikon F-mount camera, be aware that you won't be able to focus to infinity. In fact, you will probably be limited to focusing at a pretty short range. I can't remember off hand if some M-mount adapters have a diopter lens in them to allow for infinity focusing, but this would degrade image quality anyway.
Besides, there are lots of excellent Nikkor lenses to choose from. Why waste money on an adapter when you buy F-mount lenses pretty cheap.