Well i didn't ! I mean theirs alittle bit of the game that refers back to stuff that could of happen in the witcher 2. It also has characters from it. At time I dunno certain things that are refered to in past games however I don't really think it matters all that much. It written really well and kinda just works. If you have the time I would say play it
However I didn't and I'm enjoying it alot. The game is quite long to with all the side missions etc so it really up to. To try and do everything in the game is nearly impossiable because it so big and the smallest dissision turn up in cut scenes etc. For example I killed these people in a tarven in the frist game nothing happend. 20 hours later the lady was like this bastard killed people