I recently did the same, myself, not having flown Frontier, since it became an Ultra Low Cost Carrier (no frills). My flight departed late afternoon, on a weekday. The check-in line was rather long; however, they were very efficient at getting customers checked in with their bags - it did not take long to reach the counter. I can't imagine it taking more than 10 minutes, if that, to drop your bags.
Be prepared to bring your own snacks and beverages, unless you don't mind purchasing them onboard. The only complimentary beverage is tap water.
Since I paid extra for "The Works," I was able to board first and sit in one of the first three rows of seats, which had lots more legroom. "The Works" also permitted me to change or cancel with no fees; that allowed me to cancel and rebook at a lower fare.
All-in-all, I thought the experience was fine. Honestly, the part that I liked the least was the gate area used by Frontier; it was older and nowhere near as modern or loaded with food, beverage, and vendor locations, compared to the Southwest gates.. The seating areas at the gates were also much more limited.
The cockpit and cabin crew were very good, and the flight landed only slightly behind schedule, due to very bad weather that we had to fly around.
BTW, Frontier's fleet is on the newer side.
I would not hesitate to fly them again, even without RAC, if their schedule were better than Southwest's.