I wanted to do my own long exposure test on the 5D Mark II. This is a 37 minute exposure at ISO200 - f6.3. I didn't use any in camera noise reduction or do anything in post production. This image came straight from the camera (pretty much).
It has no noise. Not only that but it's so sharp. I can count the branches on the tree that's behind the house, through the two windows. AND, this long exposure used less than 20% of the battery - so if it stays clear tonight I'm going to go and get an exposure twice the length.
I conclude that if you have any money whatsoever in this economic crisis - you must spend it on this camera.