Pretty great. Flew to and from Ottawa.
The odd thing about writing this review is that if you are a resident of Toronto, one can really not untangle the Porter experience from the Island Airport experience so take that while reading this.
1) As of March 2010, A very nice terminal with free wifi joining a very short list of airports with the free wifi (Portland, OR; Las Vegas; Denver). Free non-alcoholic drinks in the terminal (coffee, espresso (!!!!), soda, juice).
2) Very efficient check-in: you only need to check in 30 minutes early for flights from Island Airport (Toronto) and I could have probably done the same in Ottawa although they suggest more time.
3) Free food and wine on a 45 minute flight (!!!!).
4) Very easy shuttles and a ferry to the airport from downtown.
Staff were helpful and smiling but my flight was uneventful so I can't really comment on their ability to coordinate difficulties. No complaints but no opportunity to rave either.
OK, so I feel like the gold standard for North American airlines in Southwest and I think that, as tempting as it might be, comparing the two is really not possible. SW is "no frills": they get you there cheap and easily. Porter is easy but not necessarily cheap. I feel like they are really not able to do the discount thing ($400 for a flight to Ottawa?). If they can get flight prices down, they will be great.
The fact that their prices are similar to Air Canada is the only reason they don't get five stars.