You mean it would be too costly to run Dura Ace kit on dirty roads in the winter. That's the driving factor for most of us. If I was a multi millionaire my hack bike would make that Pearson look pretty average.
Back to reality, I concur that Pearson is lovely, but as I don't do cleaning I'm afraid I'd be unsure about taking that out in the usual British summer, let alone commuting in winter. 
EDIT: What does annoy me about it is the tyres! You talk about saving some weight hence the carbon frame etc, then you use the heaviest tyres you can find!
Calm down dear, it's only a nice bike!
Actually, the tyres (along with every single aspect of this bike) are very carefully considered indeed, and the logic is as follows. Robust tyres that grip like buggery are an absolute must and are the starting point for my winter wheels on the commuter. I don't know about your commuting roads, but much as I would like to use some of my superb Vittoria Open CXs in winter, my desire not to be held up by the need to fix punctures with wet/cold/dirty hands in zero street lighting significantly overrides the pleasure to be had from an extra 1mph on the average speed.
So, given this starting point of an absolute need for robust tyres, when ultimate-specifying the optimum commuter for my commute, the next thing is to identify the lightest super-robust-grip-like-buggery tyre which will help absorb the vibration from the dismal road surfaces and the tiresomely numerous cattle grids encountered (i.e. needing 28mm actual width rather than 28mm nominal width - hence the '32mm' Top Contacts). Top Contacts seemed to be the most advanced super-robust tyres, coming in at 500g (with folding bead) c.f. a lot more grammes in other super-robust tyres.
Therefore, far from being a daft choice to run on such a light/responsive commuter, these tyres are ideally specified for the task in hand. The argument that having 500g tyres means the rest of the bike should not be as light as possible is rather specious, I'm afraid. Having 300m of elevation gain each way means that shedding unnecessary weight (500g tyres are rather necessary, as demonstrated) makes absolute sense. I'd love it if the day was longer and I had the time to drag out the long commute, but I don't, so since I have to add a few hundred grammes for the tyres, it's nice to be able to take it off again by using Dura Ace and a Tubus Airy rack and a carbon seat post etc etc (yes, I know the tyre weight is rotating weight and so has a greater effect, but the theory is still valid). I did select an Ultegra cassette, though, for better wear in wet/gritty conditions.
I don't really agree with the various comments about dirty roads meaning running |Dura Ace has to be ultra-costly. The answer is to clean the bike! This applies to Dura Ace, Ultegra, 105 and everything else all the way down to SRAM and Campagnolo (
). Having nice components means there's an added incentive to do that all-important cleaning. I have pretty dire roads, in terms of cleanliness c.f. city streets, but a decent weekend clean and the occasional mid-week wipe/re-lube of chain is perfect to keep Dura Ace in top working order. Are you all riding through slurry pits and quarries or something?
