I have had the offer for the trial on the two reservations I have made, but since it is only good starting with the next reservation, I passed simply because I do not intend to fly them on a regular basis (and even if I did a few day trips, it would not include anything other than the personal item).

I had to go to D/FW twice in the past week on short notice day-trips, so I only had the personal item to contend with. One of the trips was booked online about four hours before the flight and was $135ish R/T. Checked in at the airport and took a seat in the 4th row each time at no cost...legroom was comparable to UA E+ but the seat was still as uncomfortable as the one mid-plane I had in the equivalent to E- (would hate to be stuck in it for a DFW-TPA flight duration as the 45 minutes was uncomfortable enough).

The key to selecting your own seat at no cost is to hold off on checking in until you GET to the airport and then just hit the kiosk. No discount for the 'big front' though by waiting...did not think to check and see if they had any more padding, although if they do, then perhaps the extra $35 is worth it for a flight like DFW/TPA or similar duration.