If buying the extra seat, ya probably should avoid the bulkhead row or the exit rows, as those have the immovable armrests. Much better to try to get row 2 or 3.

I've tried to quarterback the seating as well (with status you can get a free seat assignment except stretch and the free "upgrade" at the check-in window). The batting average lately hasn't been so great because they've had some rock-bottom sales lately (it's a slow period) and that has attracted a lot of late bookers, with the singletons among them not wanting to pay for a seat assignment.

So the seat map even early on the day of the flight has often had a fair number of empties showing, whereas the actual flight takes off close to 100% full. Frontier seems more willing than others to leave the sale fares up (like $40 for ATL-LAS OW on a Tuesday) and bookable on just 2 or even 1 day's notice rather than raising prices close to flight time at the risk of the seat flying empty. The latter strategy, which most airlines and I think even Spirit does, is to keep last-minute business travelers from getting a bargain. Even though ULCCs don't have very many business travelers.