We flew to Vegas in January. We took Allegiant. They are all direct flights to destination cities, so no layovers. However, they only go a couple days per week. Not daily. Soooo.... we get on the plane at 9:00pm. They de-ice the plane, and then it has "an indicator light problem". So they push us back to the gate and we deplane and wait for the mechanic. Everybody runs down to the airport bar. It's closed and so is the snack bar, because we were the last flight out that night, and all workers went home. There are no drinks available. The airline is supposed to give us some, but they can't bring any through TSA because.... we were the last flight out that night, and all the TSA staff went home. Eventually they got a Sherif to get the drinks and bring it through a secure area.
The way Allegiant is set up, the crew lives in the destination city. Vegas, Disney areas, etc. They fly out and back once or twice a day, and then they're out of time. They can't fly any more that day. They don't have spare planes or crews they can send in a reasonable amount of time. So you either wait for the plane to get fixed and hope the crew has enough time left that day, or you wait until the plane is fixed and wait for them to sleep X hours, or you try and book on another airline tomorrow.
Fortunately, mechanic shows up, corrects the issue, and we take off 3 hours late. Since there's no connecting flights, things work out OK, we're just a bit more tired before we hit the town.
Otherwise, I've never had problems with Allegiant's service. That was a mechanical issue and could happen to any airline.
I'd recommend them if they are available in or near your area, and if they are going someplace you want to go.
