Yeah, my backup has been my old Canon 5D Mk II. But I don't reach for it any more, outside of specialized circumstances where something about the Canon system makes it the better choice. (E.g. wide angle T/S lenses.) Otherwise, I have become utterly spoiled by the Pentax images and absolutely view the 645D as my primary system now. Of course, there's not much point having a backup system that I don't want to actually use
, or don't even have with me when traveling due to the issue of doubled-up load of lenses & accessories.
Based on that, I picked up another 645D body; low mileage, formerly owned by somebody I know & whose treatment of equipment I trust.
I used it to finish shooting the project I started in Arizona, while sending mine to Japan. Most likely I will keep the 2nd body once mine comes back. There is nothing like a pro level service offering from Pentax in Canada as far as I can tell; from what I heard the entire Canadian 645D loaner pool is 2 bodies, and both were out when mine went down. Pentax Canada would have been of minimal help anyway since I was in the USA at the time of the failure, and I was told the Canadian warranty was of no use to Pentax USA. On the whole I was underwhelmed by the customer service aspect of things. This is definitely an area where Pentax could improve.
I dislike the idea of being without my primary system for weeks or even months. Since rental costs would pay for a 2nd body after a short period, I figure I'm simply a 2-body 645 digital guy now...