I've also used them to fly from Bellingham, WA, to Las Vegas. They were a great airline for us, and saved the hassle and expense of driving to Seattle, then parking at SeaTac airport. I haven't flown them in a couple of years, so can't speak to the up-charges others have mentioned, but even so, their rates are so much cheaper than the big carriers flying out of Seattle, the fares are still better. FF miles notwithstanding, next time I need a direct flight to somewhere they fly from Bellingham, I'll use them.
My only issue with them is their schedule - they only fly to certain destinations on certain days. That doesn't always fit my travel schedule.