FWIW, I've flown Southwest, AA, and Alaska out of OAK with some frequency. Both AA and Alaska have always been quite smooth, and the AA crew at OAK (the TAs go back to be the GAs) have been stellar. The Southwest staff have typically been friendly and energetic. The Southwest experience out of OAK has been fine as long as you don't have to check baggage, but if you do have to check bags, sometimes the waits have been 20+ minutes during peak times.

-Hayden