Ture,
I just got back from a 3 week trip to Kauai and brought my 4fun out there. I had never really done much surf kayaking before and thought it would be fun to have out there.
Ultimately for the hassle, I probably wouldn't do it again. At least with that type of boat. You really need a "wave ski" or some sort of surf specific type of boat.
Another very important thing. The whole time I was there I met ONE guy that is apparently the ONLY guy on the island (at the time) that does surf kayaking. The climate is not very accepting of the idea yet. Kauai is a very locals type scene and you don't want to paddle out the wrong place. I was told that some folks will really give you a hard time, although to be honest, I personally never got too much crap, but then again, no one would even say a word to me... even if I just said hi.
In most of the good surf areas, you have to paddle pretty far to get out to them and if you have to swim for a myriad of reasons.. you are totally screwed if you don't have real good backup (ie another paddler!!).
Call me if you want to chat... 303-517-2621