Look at the google reviews for the various superchargers. You'll get a good idea if it's busy or not, if there is a wait, or other gotchas, like if you have to pay for parking to access it, etc... I did this on my last trip to Canada, and found it to be pretty spot on. The only SC that had a wait, was the one in Richmond, BC, but it was exactly like it was in the google reviews... Busy with line on Friday/Saturday, but pretty easy to find an empty stall in the middle of the week, etc...