Pros
Salary is one of the best outside of oil & gas / finance sectors. Some (although can be few and far between) fantastic engineers to work with and learn from. Work/life balance is OK - expect busy periods and some quieter periods, much like any other job I've ever had. Flexible working arrangements are possible, depending on your particular role. However, if you do ever work from home, beware of the obnoxious views from other older colleagues. Looks nice on your CV.
Cons
Small fish in a big pond syndrome. A lot of the promises the company sells at interview stage aren't true. You will not be able to influence what goes on in the company, instead you will be attacked with 'this is the way we've always done it' and 'oooh - that sounds a bit risky'. Despite my 2 years of trying, I'm sadly having to finally succumb to this attitude just to get on. Progress reviews and development plans have, in my experience, been useless. Objectives and goal setting are great, but there is no push to achieve anything outside of your job role and its all very generic and corporate. Travel and Parking is a disgrace for such a large corporation