Don't know if I'm just being unreasonable, but I HATE the Planar Champion prestige class from Manual of the Planes.
It gives supernatural abilities without any pre-requisites, several of which make no sense (given the limited Ethereal and Astral connection in the OUter Planes), and a Planar Survival ability that's very powerful, lasts indefinitely, and cancels out the broadranging effects of planar travel in a way that even higher-level spells don't.
This strikes as utter munchkinism and an attempt to evade everything that makes Planescape unique.
Have I just got a bee in my bonnet, or does anyone else agree with me?
3e Manual of the Planes has about the same to do with Planescape as Forgotten Realms Campaign Setting has to do with Tolkien's Middle Earth. So don't take it too seriously. Personally, I just use it for updated statistics, such as how much damage a sod frying in the Plane of Fire takes per round. What particularly infests my own headware is the sheer number of minor changes MotP has - tiny little things like leaving out the entire bloody Olympian pantheon from Arborea, Modrons from Mechanus, and all Para- and Quasi- Elemental planes. But then I go back and think about what I wrote at the beginning of this paragraph, take a deep breath, and go back to the 2e books.