Hello,
I would like to add my disagreement with the new duel system as Akashani and Stylee said with more technical arguments.
Thanks for your attention,
Best regards! 
There is no new dueling system. As Stylee already said, there was a change to prevent you from claiming an NPC from far away. As a side effect (or the choice of allowed distance), I can see that dueling is less fun. You will just have to wait for some devs to:
1. notice that this is a bad side effect (as is the fact that you probably can no longer attack the mercenary behind the fence in the arena)
2. find a way to fix this
3. find the time to fix it
With all the other problems that you all noticed, the last one may be the most difficult
Oh and about the lag: I have an intel graphics chip, and it is not unbearable at all. Actually, in most cases things run better for me (I did timing comparisons between old and new maps). THe lag seems caused by looking in directions with many polygons, such as the city. Grass does not help, but is by no means a cause of the 'unbearable' speed. As ThomPhoenix already said, these things are known, but may also be related to Crystal Space. It will just take some time to find the cause and a solution.
edit:typo