Ya, I have flown about 3 times with no trouble upgrading. It helps also that AS has added the little diamonds to the web reservation page. Helps in choosing flights.

On my last flight I was traveling with both my wife and Brother-in-law. Now I know I can travel with one passenger and upgrade with no passes but figured I'd need to use my guest passes for my brother-in-law. To my surprise they never asked for the vouchers from him. In fact I noticed that on my boarding pass it still had the "Collect Comp-Upgrade" printed on the top which of course I didn't need. I am curious if they arent collecting the passes because they can't tell who should give them and who shouldn't? This happened on both the outbound and return flights.