I bought a supersix evo HM frame from Paul’s in the spring (2015 model) and built it up using the ultegra groups from my old bike and added some campag Bora carbon wheels. Utterly brilliant bike, really really fast, light (6.9 in current build for a size 58) and also far more comfortable that my ‘endurance’ carbon roadie before it, and way more comfortable than the obscenely expensive cervelo R5.
It’s racy yes, but if you get it fitted by a pro it doesn’t have to be uncomfortable (don’t slam the stem) but the biggest thing I love is how it handles, it’s so precise and secure at speed it really builds confidence, but also doesn’t bite when you’re tired. I’ve ridden mine in the alps, done the dragon in the UK and just blown away by it. Yes BB30 is a pain and yes the cable routing is external (will just HAVE to buy etap if going electronic) but blows the socks off every other carbon ‘race’ bike I’ve ridden, which is a few!
Scarily, the 2016 is supposed to be better. If you can find the frame though, custom is the way fwd.