I just finished my first play through of AP, and seeing as it's created some polarizing opinions I might as well give my thoughts on the game. I've never played anything by obsidian or bioware (unless you want to count fallout 1 and 2), so I suppose I could either be a neutral party or have no idea what I'm talking about.
Anyhoo, while I did enjoy the game, I felt like a major problem with the game was that it couldn't decide how serious it wanted to be. The combat is obviously meant to be a stylized spy-action sort of thing, with little regard to 'reality'. The problem is, with the exception of a few characters (Sie, Brako and Steven are the only ones that come to mind. And Omen Deng to a lesser extent), almost everybody is rather serious and normal. Neither of these things are bad on their own, but when you combine them together with a mediocre story, the result is rather messy.
In terms of the actual game play, which I imagine is more important to most people, it was decent. The stealth system was solid for an RPG (even if that's not saying much), and I didn't notice anything particularly bad with the shooting mechanics or AI, though neither of them blew my mind. I thought the dialogue system was the best part of the game, and I am kind of confused that most of the reviews ignored or dismissed it. The writing was creative and well done, especially compared to RPGs like Oblivion or Fallout 3; even Mike's snarky, sarcastic comments were usually entertaining to listen to. Plus, it was implemented as a primary aspect of the game play with the C&C, which was very impressive to me.
Overall, I liked AP. It had some problems, and the ending was terrible, but I like it enough that I'll probably replay it again. Considering that I rarely finish games, let alone replay them, that's good enough for me.