I felt like KOTOR 2 really suffered from not knowing which ending to KOTOR 1 you picked and having Reven be an AFGNCAAP. These are events that completely redefined the galaxy and you aren't told which way it was. I feel like it undermines the notion of control since apparently it all turns out the same way regardless of what you do.
I really didn't understand Kreia's philosophy or why that was supposed to appeal. I really, really didn't like the way they invented the concept of the player character being a to explain the leveling up phenomena. Sure rpg leveling up is cliche but the last thing Star Wars needs is another bit of phlebotinum jammed in there. It's not just that the camel's back broke, the phlebotinum piled up on that camel corpse is a freakin' tower to heaven.
Kreia was Obsidian examining the ridiculousness of the stark black/white good/evil divide of Lucas' universe.
She was rejected by both the jedis and sith becauseof her heretical beliefs that "the will of the force" was some sort of malevolant being that needed to be destroyed. She also had to rely on the force in a huge way because she was blind I think? It's been a while since I've played it, but like most Obsidian characters/writing she's far and away deeper and more nuanced than the characters in the original Bioware game.
Both the Jedi and the Sith believe the force and life are intertwined things that cannot exist without each other. Kreia believed this was horribly wrong, and that the force itself used sentient beings as pawns in some sort of attempt to maintain balance or something. She also belived that future generations of force-users should abandon the jedi/sith orders and extremes, though I think as a stepping stone to a complete eradication of the force. She was an evil-leaning morally-grey character, but with realistic motivations and flaws.
The force vampire thing is a really odd sticking point considering all the other stuff that's happened in the Star Wars cannon. Especially since Star Wars is basically nothing but phlebtonium. Seriously, the entire series and almost everything in it is stuff like this.