I flew stand-by on a buddy pass when I went to the UK last October. I had a reservation in the system for my return to the US, so I printed that out and showed it to the I/O and explained I was on a buddy pass and I didn't have any problems.
If you're going over as a visitor, I would just make sure you have a reservation to fly back to Canada to show the I/O and I'd make sure you were put on the list with plenty of time leftover before your visa would expire (because of potentially not making the first flight). I was even able to check my bags and had no problems with picking them up on either end of the trip.
If you're thinking about doing it to go join your husband on a spousal, I'd go for it, since you don't need a return trip for it.
PRO: Cheaper, much cheaper.
CON: Not being able to pick your meal (you get whatever is leftover after they feed everyone else in your class), but the people on United were accommodating with my food allergies anyway.
CON: Not being able to give the person meeting you an exact time. You'd need a way to reach them to let them know if you definitely made the flight.
But I'd still do it just for the money saving part!