I was cogitating on this and why it is that I love the Tricross so much when riding earlier, although it would probably apply equally to any other psycho-cross bike.
I think that it's because the bike is not specifically for one thing, it's not built down to a weight, it's not built up to a downhill, it's just a bike that you can do stuff on without being too worried.
I had road bikes when I was in my teens and I had no worries riding them around the farm. They were strong enough to take it, they had tyres that didn't puncture at the first sight of a stone, you just got on and went for a ride.
It appears, to me, that the ethos behind the CX bikes is the same brought up to date. Road bikes are faster on tarmac, MTB's are more comfortable off road, I have both of those but most of my rides, like today, are a mix of roads, paths, pavements and mud tracks, hopping kerbs and riding through decomposing leaves, branches and twigs that have fallen off in the winter, just doing it.