I "cheated" on Frontier with SW twice this last year, once due to a route that Frontier didn't fly, and again due to significantly better price/schedule. SW comped A-List status to Frontier FF's for the end of the year so I got to experience their elite experience as well.
Results:
Trip 1 was OK, despite status I waited for 45 minutes at security in PIT as no one was checking/enforcing the elite line. Also I found the whole seating process very stressful, was flying with a companion who did not have A-List status and didn't know how it would work out (it did, but I hated the uncertainty of not knowing whether we'd be seated together).
Trip 2, arrived in LGA at the crack of dawn, only to sit for 3 hours due to a mechanical issue before the flight took off. No apology, voucher, compensation, or anything else sent after-the-fact.
The verdict:
Unless presented with overwhelmingly better fare/schedule or a route which F9 doesn't fly with no alternative, I would not choose fly SW again, now that the free elite status has expired.