Seren: Though i never personally got into killing guards because it seemed so utterly pointless. There is a distinct lack of humanoid combat in my opinion.
The majority of such combat scenarios are always in scripted battle scenes where Geralt has an AI companion screwing up the flow of battle. You hardly ever get to test your combat prowess with Geralt versus 6-7 humans,steel v steel without some sort of "help".
*potential mini-SPOILER*
In fact,one of my favourite fights in the entire game is during the Malena quest in Flotsam,where you get ambushed by a group of scoia'tael.
Basically,it would be nice if random bandit groups spawned consistantly in the wildnerness of the differant chapters or even within Flotsam itself at night. For me,whenever the thought of attacking the guards crossed my mind it was due to a wish for more humanoid fights.
Well there are some random bounty hunters in each act though. And there are some bandits in the swamp area in Chapter 1