I can tell you that I used John Horan once to survey a boat for me (picked him out of the NAMS website) and he caught a major hull problem on a boat I was buying. I remember the day very well because it was a heavy snow and he kept on going and took the survey very seriously, even though he must have been cold as rb2@gr5t#$% tapping that hammer for several hours.
I also know Andrew Barrends (Tri-State Marine Survey 410-963-0063) and he seems to be very knowledgeable. He's doing a post purchase survey for me know.
Regarding a new boat, don't assume there aren't any manufacturing defects or poor assembly on the new ones. A new boat may very well have more problems than a boat 1-2 years old where the problems most likely would be worked out. I would definitely survey any new boat given the money you are spending. You will probably get the investment back right away. Dealers are much more likely to fix problems before they get all your money.