I use a Nikon D40. It's a great unit for the price and uses the same sensor as the QHY8's. However, there is one feature of the Nikons that drive me insane, the 'star-eater' settings. See Covington's MODE 3 work-around, but it's fiddly:
'turn noise reduction on, and then turn the camera off while it's taking the dark frame after the main exposure. Naturally, you'll have to take a dark frame of your own (the same way) and do the subtraction on your PC when you process the pictures'.
With this in mind, I think that Canon's are better suited to AP.
See Christian Buil's and Michael Covington's articles for a full discussion on this issue:
http://www.covingtoninnovations.com/...508/index.html
http://www.astrosurf.org/buil/d70v10d/eval.htm
Logan.