BA trained me, and gave me my first job, on shorthaul on a jet. I then got the chance to fly the Jumbo with them, and saw the world (albeit briefly). I've now just got a command with them, after 8 years, so the "twenty years to command" stuff some have written is patent bollocks.
No, it's not perfect, and LHR is a right pain in the ass. I don't know any different, as I have only worked for BA, but from where I'm sitting, I wouldn't leave my current job. And of course the longer you stay in any job, the harder it is to leave, with incremental payscales, seniority etc.