I have been rebooked several times in the last month (from ONT to SFO, e.g) and didn't get the SSSS. I even volunteered my seat in Fort Wayne on AA and was taken and put on a United Express flight an hour later. I was sure that this (changing airlines, one way) would trigger the SSSS (that's what I had always been told), but it didn't. I have used the Easy Check-in at ORD about 10 times and never got the dreaded SSSS, even with an upgrade. BTW, it seems that almost 50 percent of the time the machine will tell you to go to an agent to complete the transaction if you have an upgrade confirmed (which I did on every use of the machine). So inconsistency is still consistent with United.