Despite completing it last week, I'm still playing Alpha Protocol - I've rolled a Veteran character now that I unlocked the option, and am blasting through with a mix of stealth, pistols and shotgun in an attempt to explore the story a bit more and mop up a few more achievements.
One of the greatest things about Alpha Protocol's dialogue system, which relies on the player picking a "stance" rather than specific replies, is how unpredictable it is. While the dossier you've accumulated on another character might indicate they prefer a no-nonsense attitude, there's no telling for sure if the Professional option will have the desired effect on their opinion of you.
This does make it a bit more difficult on subsequent plays though, especially if you're aiming for specific opinion-related achievements (not to mention, chasing a negative reputation with someone can result in limitations on intelligence and supplies). I'm trying to get Steven Heck to hate me, but I always seem to end up picking options that even out to neutral.
Part of what makes it difficult is that your conversations with other characters will give a new acquaintance a preconception of you, which results in some opinion-altering exchanges that you can't directly control.
I was kind of hoping that in addition to the veteran, shotgun and remaining romance achievments (as well as a couple of plot-related ones) I'd be able to pick up the two hate-related rewards as well - but it seems I'll have to give it at least one more playthrough (possibly with a guide) to actually get those.