Mudguard report: i've ridden in torrential rain, fresh snow and thick, slush, and my bike looks like its just been cleaned (except the wheels) I was regretting going for the 60mm over the 50mm, as they're a real pain to fit in the frame (and still need a bit of tweaking), but I'm now pleased to have chosen the wider ones, as they work so well. Previous bikes I've owned have only ever been set up with fenders slightly wider than the tyre, but the little bit of extra width makes a huge difference to their performance. Very pleased with the flaps too- the front one keeps my feet very dry, and the back one is the perfect height, so it only just scrapes during wheelie (this should be the industry standard way of setting the rear mud-flap height).
Edit: still riding on the horizons, as the other tyres haven't arrived yet, but they actually gripped better in the snow than they do on wet tarmac (Not hyperbole, there was literally better traction). Looking forward to some better wet tyres, but for now I've re-assembled my old beater with a set of schwalbe winter spikes on. The roads around here can be pretty treacherous, and I'll just ride that when it gets really icy.
Edit 2: my prediction for the future of wet weather cycling gear is: everyone will eventually realise being warm, dry and comfortable is way better than looking good, and start riding in ocean racing oilskins, paired with neoprene overshoes.
PS. I took some proper photos, on a proper camera, in the snow. I'll put them up when the film is developed.