As said, it's pretty much the same game as D&D 3.5; some parts are better (skills and combat maneuvers are simplified; the paladin class is greatly improved), some parts are much worse (spellcasters are even more overpowered compared to non-casters; there are feats which don't actually do anything). You can typically use 3.5 material in PF and vice versa, and it's recommended you do so;
Tome of Battle is probably the 3.5 book most worth looking into.
If you have trouble getting your character to do what you want, post
here or at
Minmaxboards for advice; D&D 3.5 is the main focus of both sites.
EDIT: Also, I don't know in what form you're viewing the rules, but
psionics are basically MP-based magic and/or ki-users, and better balanced than the standard classes (most third-party publishers are terrible, but Dreamscarred Press are probably the best writers around). They're worth checking out.