Let me show you the result of my 2D drawings on the first page of this thread
http://www.yachtforums.com/forums/28649-post15.html
We have now launched the first boat and have made a few sea trials. It performed better than predicted, which is nice as it is my first complete design including the hull. She was doing 46 knots and still hit the rev limiter with the biggest props available and she is cruising 40 knots.
The interior also came out well and at the recent Stockholm Boat Show people gave us compliments all day long for utilising the space to the best.
All of this was concieved in 2D with no need for 3D except for running the CNC-robots for the plugs.
My conclusion is still that (with a little luck) what comes out is what you put in. No more no less...
(She is 40´= 12.50 m x 3.65 m, displacing 6.5 tonnes light with 2 x Volvo Penta D6 350 DP)