The last time I flew Allegiant I remember it was TRICKY to book the flight and not have that sneaky up-sell of the hotel shuttle thrown in! IIRC the trick to removing it was not obvious.
I have not flown with them lately, as they pulled totally out of LNK and do not serve LAS out of OMA.
We did try them once out of GRI (~120 mile drive) but the savings over Southwest did not justify the hassle of that long of a drive.
In all fairness to Allegiant, I never had any issues, but our company TAs did warn us of the reputation they had in the travel community, such as pulling out of a market at very short notice (it happened in a few years at LNK), very slow refunds, and leaving customers high and dry in case of a cancellation.