I love Foltest. He, and really, the other Northern Kings, are all great. Henselt was a pleasant surprise as well. Yea, they're all bastards from any modern point of view, but taken in context of the setting, I love 'em all. :p
The sheer confidence they all radiate shows you what it took to be a leader of men in such an environment.
When Geralt relaxed by the window, I was like, "oh fuck, the king is going to die". Still, Letho showed some real class by letting the children get out of sight first. Can't say Witchers are completely heartless. :p
As an aside, who else laughed at Foltest's expression when Letho (as a priest) told him it was time to pray? That so embodied the typical leader's kowtowing to religion, even in today's modern society, that I almost spit out the coke I was drinking at the time.