If I can add my .02 cents: The yellowhead in Manitoba was quite nice (good pavement, super wide shoulder), but once it ends in Portage La Prarie and becomes the TCH heading towards Winnipeg, it's a nightmare, just as described above. Northern Ontario on the TCH was just fine, if my memory serves me well. I was warned about completely broken-up road surface, and found it to be prefectly smooth with a consistently decent shoulder (two or three feet). Traffic never bothered me much. Except for tractor-trailer trucks, but then again, they made me nervous everywhere.

And I fully think you should do Ontario instead of Michigan. Northern Ontario is so spectacular!