Re: Niall - agreed. I went from being a rebel without a cause but with a heart to the right hand of an oppressive regime in the space of a few missions. I wish there would've been a bit more transitions in place, as I was suddenly destroying whole villages without much of a reason beyond "swarthy dwarf shows me a box of Molotovs and we're off".
In fact, as I think of it, the whole storyline of the Mexican campaign seemed dodgy, with the player going from assaulting the rebel's mesa base and killing all their dudes to becoming a hero of the Revolution in the space of a few missions. Not that I wanted to stay longer watching important NPCs randomly drop dead from rattlesnake bites then appear later to hand out a mission or two, and I can understand the whole "revenge makes a man do revengy things" bit, but the whole section just seemed to be overly amoral just to show everyone how awesomely amoral one can be.
Loved the ending, though. Just felt right.