I want to add:

I've still been flying AS SEA-SFO/SJC (and will still be doing so for another couple of weeks). I always talk to the person sitting next to me about whether or not they will be switching like I am. Most everyone has said that they are trapped with AS because of the frequent flyer program.

If VX doesn't offer something compelling for FF, I fear that it will be tough to get these people to switch. For me, the amenities are worth it, but for most people on short hauls, it's not.

I don't think they can beat AS with fares and frequency...