I'm keeping an eye on Frontier Airlines, which has grown its nonstop service out of SFO, now including SFO-DEN, SFO-LAS, and SFO-LAX. Plus, JetExpress service out of SJC. Their frequencies are typically much lower than WN, but the crews I've encountered have been friendly, there's IFE (if that's your thing).

If you're frequently Bay Area-DEN, Frontier does have much better frequencies out of SFO (6 non-stops, 5 1-stops daily) than WN out of OAK (0 non-stops, 8 1-stops).

Otherwise, I fly AS where I can on the West Coast (or AA to LAX and SAN).

-Hayden