Ventajas
Good culture and team work across all sites in the UK. They are investing in staff development more-so now, and are modernizing somewhat with the use of social networks externally and internally. I worked for RSA in the UK for 7 years and did enjoy my job. There is a reason they rate highly in the 'Best (big) Companies to work for' in 2012,13 . They are really supportive to any personal issues you may have ie long term sick, etc Good HR department. Reasonable benefits (insurance staff discount, pensions, sharebuild )
Desventajas
The usual office politics. The structure needs sorting out - as in team structure - some areas have vast amounts of contractors, when there are internally great staff that can do the work . I think they sometimes struggle to realise this. This could be true of any large employer though.