My last JFK-OAK flight was on one of the oldest A320s and diverted to LAS (one of the only diversions that day last year). Extra annoying that on top of shifting their Bay area focus to SFO, even if the one flight a day (to OAK or SJC) works for your schedule, if you don't want to risk a diversion in winter you have to fly to SFO.

Of course then you have to worry about delays there but that's another story.