I used to work for someone else, and even though I loved it, I am happy to be at BA. Would certainly not consider working for a loco now that I am where I am (unless I didn't have a choice). As far as longhaul goes, with the 767 picking up some of the East Coast routes, the 777 will have better rosters in 6 months to a years time I reckon. The Jumbo is the fleet to be on though I would say.
I fly the 767 and I love it - although I am on the newer side of things.
If you are aware of the pension and retirement age legislation possibilities and you have your eyes open, then I reckon BA may well be a good choice. It depends where you are now.
The atmosphere is good generally and when you are away from LHR it is as fun as you make it. At LHR things can go very well, but there are too many occasions of niggly annoying things. If you let it wash its OK, if you are prone to getting annoyed by it, then be aware!