Pathfinder was released in 2009. Since then it grew with the addition of many books. While adding new stuff is great I won't be surprised if a lot of revision had come along. And since those revision are harder to keep track of, so...
What are those rules that have changed drastically* trought the years?
For the purpose of having a clear scope I'm manly interested in the changes on the Core Rulebook, GameMastery guide and Advanced Player's Guide since their respective release date to today, but if you want to expand beyond that is always appreciated.
*I don't need a complete errata list, I prefer the focus on bigger, gameplay impacting, changes
A bit of Background: I'm about to join a group which play pathfinder, and while searching for guides (I like to have an idea of how things work at best before I can build my character how I want it) and for edition differences (I come from playing manly 3.5e) I realized that many of the old tips and consideration won't be always valid since the game is still growing, making the whole re-learning harder.