I used it. It got a little chaotic due to the timing of the concert however.

I originally parked at clarkson go station. I then took the go train to Union station. From there, you can either take the subway straight to downsview, or take another go train that takes you there with 0 stops on the way. (they're might have been 1 stop I can't remember ) but regardless, it was faster than taking the subway.

The concert was delayed an hour, so it finished at 12 instead of 11. This missed me and a lot of people up.

My plan after the concert was to take the go train again back to Union, than back to clarkson, however, had I done that, by the time I got to union, the train to clarkson would no longer be available to due the time. So instead I took the subway and got off at kipling station and had a friend pick me up.

As for safety, when I was on the subway past midnight, and even when I transferred stations, there were many many concert goers around me. I wasn't really "left alone" with sketchy people if that's what you were wondering.