I have been very lucky to have been upgraded a few times in the last couple of years by a number of airlines mainly BA and BD. The best was when my girlfriend and I flew back from NY this Feb. The check-in lady noticed my girlfriend's diamond ring and complimented her. My girlfriend went on to explain that it was new as I had proposed over the weekend. The lady then said 'wait' and tapped away on the keyboard and handed over some business class boarding cards with a huge smile that was matched by my now beaming girlfriend. I'm always very grateful to the groundstaff for things like that and as small token of appreciation I always rush off to buy the biggest tube of Toblerone in the shop for them.
It's a real shame that these days pax are so demanding and ignorant of the FAs. I think they do a great job given the number and diversity of tasks they are expected to perform. I often travel with my girlfriend so we take it in turns to go to the galley to fetch drinks but most of the time we carry a bottle of water anyway.
Anyway, to all cabin crew; nice job and always well done! Look out for my girlfriend and me - we always have a competition over who can hand back the tidiest tray, it always makes the people sitting next us laugh.