I have to go to BOS in early November and if this keeps up I might just take UA via DEN and clear US customs in YYC. I have been toying with using my SSWU's for this trip but I think I could manage on UA with E+ seating and 100% miles if it means missing the nightmare everyone is describing in YYZ.
I don't want to get stuck on RJ's or Dash-8's out of YUL and YOW if I am using a SSWU.