I successfully booked some tickets, but it took many hours spread over many days. I was doing a simple bush Alaska-Lower 48 round trip. They do not allow you to book any flights operated by Horizon, which very much limits the ability to book. (Perhaps that has changed. If so, that's great news.)

Everybody was very nice, but it was a massive time waster. Interesting learning experience, though. I'm not in any hurry to try it again!