Pros
From a researcher point of view, STFC is an excellent workplace. It's a world-renowned laboratory in the fields of photon, neutron and muon sciences, biosciences, particle physics, high-powered lasers and space sciences. The atmosphere is informal, there is a very large amount of seminars and training available to improve your knowledge in technical subjects. Office space is not cramped (usually 2 scientists per office). The IT infrastructure is fulfilling my needs. The canteen at the site usually serves tasty and good quality food. I grade the bureaucracy at STFC as the best one I encountered so far in the different laboratories I worked in: procedures were well organized and administrative staff was efficient and helpful.
Cons
RAL is located in Harwell Campus. The site is in the middle of the countryside, far from larger cities, the largest town nearby being Didcot. If you wish to live in larger, more active, cities you'll need to commute with a trip time around 30-40min from Oxford, 40-50min from Reading or 1:20-1:40 from London. The career advancement opportunities inside STFC are somewhat limited.