Pros
Good and professional colleagues in a not too competitive environment. The energy sector is going through an interensting and exciting time of change which is really good to live working for one of the main international players. The working environment and culture are rather laid back and respectful of the work/life balance. During te latest years much has been done to change the corporate culture from a state owned monopoly towards a more "open" approach: climate surveys, bottom up innovation processes, which give a sense of better employees participation in the direction the company should take. The firm is big and the business rather stable so employment is almost entirely based on open ended contracts. So, as long as this is what you look for, this might be your place. Moreover, you get some opportunities to have an international career path if you want.
Cons
The downsides of "being in the process" of changing culture is that change is actually yet to come. Being a huge ex-monopoly, the company is still bureaucratic and struggles with its intrinsic inertia. The approach to personal growth is questionable. Promotions are mainly based on age and rather slow. Considering the overall National market conditions, the pay is decent, but really not a bit more than that.