When I regularly used to travel MAN-YYZ the cheapest fare was always via Philadephia and Baltimore with US Airways. Was always a pain on the outward leg with the two changes of aircraft, but on the way back I'd always get to the check in desk at Toronto where the staff would comment on the "weird routing" and book me direct to PHL. Was always a good £150-£170 cheaper than any other route and around £200 cheaper than MAN-PHL-YYZ with US. Throw in the cash for the voluntary stand down at PHL on the way back and it was a very economical way to fly. If you're in no great rush, and enjoy the airport environment (sad, I know) it's an interesting way to get from A to B (via j and m).