Originally Posted by alanh

Just as another data point: I'm on 1198 PHX-PHL tonight. I checked late last night right inside the 24hr window, and the site said no upgrade available, with the link for being added to the upgrade standby list. As the site was running really slow, I didn't complete checkin then.

I went back to check in and get my boarding pass this morning and to my surprise I had the button offering "complimentary upgrade". I clicked it, of course. So I don't know what happened (not that I'm complaining!).