This is all pretty interesting. We sent in our UPCs only a week before the end of the promotion--Jan 31, I believe--and got our gift certificates around 1 April.
As for SWA booking: We checked for the cheapest fares on-line first, then called SWA to reserve our flights. After that we had to drive to the airport to redeem our gift certificates.
Later on...twice, in fact...our fares went down. We simply drove to the airport and received vouchers for the difference. The vouchers are good for one year to fly SWA again. I believe we will have to book and redeem the vouchers within the year, not necessarily fly within the year. Correct me if I'm wrong.