In reply to dazwan:
This weekend, I went for the first proper ride on my roadbike since December. Lovely to ride it again, and I can notice the lower weight over my commuter BUT for riding to work through central Sheffield on the utterly crappy surfaced roads full of potholes I want the CX wheels and fatter tyres! In fact my CX has brand new Marathon Plus tyres on it - I got a bit radical and bought 'just' 32s down from the 35s I had previously, and I can feel the difference through my butt. Doing the same commute on 25s on my roadbike would probably shake my teeth loose.
Did manage to get to 71 kmph at one point today on my commuter, so its not too slow!