Porter is the greatest. No middle seat, free booze, free WiFi in the terminal, cool uniforms on the flight attendants, consistent sales on all fares (sign up for the mailing list) and you don't have to go anywhere near Pearson.
The only negatives are that the landings can be a little rough and the taxes/fees on the fares are kind of excessive. For example, on a flight to Chicago this summer the fees on the Chicago departure were about $30, but the fees on the Toronto departure were almost $100. I really think that's more a criticism of Billy Bishop airport rather than Porter though.