Pros
Relaxed atmosphere, work can be varied, nice people in the main, job for life, no blame culture, long time scales, no pressure, if you are intelligent and competent you will probably find that you outperform most people working there easily with little effort. If you are a waster you will not be at any disadvantage. Annual inflation linked salary increases. Good pension package.
Cons
I can't speak for the entire company because it is massive so my comments should be read as applying to my experience of working as a software engineer in 3 different departments in MAS (Military Air Solutions). Software is developed and maintained in a very unprofessional manner. Everything is done on the cheap. Senior managers have the point of view that BAE don't develop software and appear to be in denial. Requirements capture, config management, testing, code reviews and practicaly every aspect of software development is done in a very hit and miss ad-hoc fashion. There are way too many incompetent staff, and at present they can easily hide and get away with shoddy work practically unnoticed by managers. Everything is done via word documents and email; we have bought into methadologies and toolsets like Rational in the past but they were never implemented properly and were scrapped. Probably because these is no proper organisational structure or framework for software development there are very limited career opportunities and no specialisations. What we have is a pool of general software engineers who are jack of all trades. Rewards for good work are practically none existant. If you are lucky enough to be acknowledged as highly compentent and ahead of your peers you will still get nothing in way of financial reward. The good staff get ground down and either quit or eventually give up trying to make a difference or making any real effort. There is no vaguely quantitative method for measuring an individual's performance and performance reviews are at best based on managers subjective impressions. Managers often have no IT background. Pay is above average for the North of England but is very low compared to similar jobs in other companies. Secretaries and basic admin staff will often earn more than highly skilled developers and have far better career prospects.