People are very approachable, and hierarchy is really just a title that people have. However, the structure is very rigid, and advancing fast is not really an option at P&G . You can easily get stuck at some management level for years (although you'll be changing roles/responsibilites within the same management level during that time). At times, promotion seems to take forever to come, even if you give it your best, and get rated top of your peer group. My Manager has been in P&G for over 15 years, and only had 3 promotions, despite being highly respected among his peers. Which is due to the few amount of manager levels (~6 Bands, you start at Band 1).
Despite having put in place some recognition for the achievement that you drive (awards mostly), it feels like achievements are not recognized for your advancement since it is slow by design. Therefore most people that leave the company do so because they end up being stuck at some management level for too long, while receiving juicy offers to join other companies from head hunters.
As an example, after 3 years at P&G, a colleague received an offer from another company with a bump of 40% in salary, and a career advancement that would have taken him 5-7 years at P&G.
Also something to consider are experienced hires. P&G is a company where everyone used to join as a junior hire. And the company is still very much optimized for this. When you are offered a position as an experienced hire, expect to be offered a disappointing salary upon joining. They expect you to prove yourself, and you could easily get 2-3 salary raises during the first years, but it'll take some great work from your side, and negotiation with your manager. Despite this, experience pre-P&G will usually be recognized less than your P&G experience.