After my flight to JFK was cancelled on December 28th, I frantically booked a last-minute ticket on Porter to EWR. YTZ was pretty empty, and check in/security took about five minutes total. (There was no one in either line.) There was a patdown and bag search before boarding, but it was quick and painless.

They did have the one carry-on rule, although it didn't seem strictly enforced on the 28th.

You couldn't get up at all on the flight to EWR, and nothing could go under the seat, but it was otherwise a normal Porter flight. The customs line at EWR was short -- we were the only flight in the customs hall.

I recommend flying Porter if you can.