I already have the 70D and PIXMA Pro-100, but I'm sorely tempted to do this.
Even with careful FoCal calibration, I've never been able to get consistent focus using the viewfinder on my 70D. Live View shots are nice and sharp, so I know it's not the lens. View finder shots just seem to vary based on distance to my subject, which is frustrating. High-speed burst is just pitiful with almost zero hit rate using AI-Servo (I understand the possibility of user error -- been troubleshooting this for quite some time). I hear glowing reports about focus and speed from other 70D owners on this forum (some after Canon repair/tuning), so I know it's possible.
If I do the deal (my rebate for the printer deal came in just a couple of weeks), then I could compare the two bodies (calibrated) side-by-side to help confirm that I might have a bad copy. If the new one works properly, then I warranty-repair the old one before selling it (full disclosure to the buyer, of course). After selling the printer and the old body, I still come out ahead a couple hundred bucks, plus a bag, more paper and a memory card.
Any reason I shouldn't do this?
Edited to add: Plus, this would mean I have a body to use while the old one is visiting Canon.