Ok, I am currently at the end of chapter 3 of the witcher 1 (via steam). Loving the lore and the world, but am starting to find it a bit of a grind. The quests are sending me back and forth across the map, and the performance is suffering on my machine. I have the second game sat here on the 360 and am wondering if I just move on? Any advice would be appreciated. Gaming time is valuable and at premium so I can't spend hours on end just to see endgame. Shall I just stick to main quest? And so forth... Thank you please! (obscure uk tv reference)

If I recall chapter 3 is when you get out of town and into the small vilage and fields right?
 
Stick to it, youre getting close to the end and things will pick up as well.
That chapter is meant as a kind of quiet slow paced moment in the game, a part where you can relax between the previous events and the final most important chapter.
The end of that chapter is kind of important to pay close attention to, and from that moment on untill the end is one of the biggest reason people think highly of the game.
 
But yeah if you want just stick to the main quest.
The is one good sidequest that i recommend however, the one about noonwraiths and one that involves Dandalion. Can't recall the name now.
Aside from that you can skip the rest.

@Tennmuerti: That is chapter 4 actually. Chapter 3 is still set in Vizima, it just opens up the other half of the city. Honestly, chapter 2 and 3 kinda feels like one chapter.

Honestly i would just move on. I loved the witcher, but i wouldn't really recommend just blasting through it just to see the end. Since you don't have a lot of time just spend it on the witcher 2 and really soak it all in. :)

Thanks for the replies! @Tennmuerti Yes I think I am impatient to start the sequel. I have decided to stick with the first game, but a couple of crashes have severely tested this decision! Also, Fez, Trials Evolution and Steam sales are getting in the way!

@craigieh28: So, did you get around to finishing it? :P