OP, if you are commuting through the week and riding for pleasure at weekends have you considered splitting your budget from a looked after second hand alu (or similar) for commuting and a decent carbon ride for weekends? £1500-£1600 is a reasonable figure to do that with.
I have indeed considered it.
I have also considered keeping my current road bike (Triban 3) as my winter hack. The thing is I only really have the space for two bikes, I already have a rigid MTB which I am not getting rid of and can double as a real foul weather hack or back up, so having just one all purpose decent road bike is the only real option.
The other consideration and the most important is that much of my week is spent commuting down what are actually really nice riding roads, with quite a bit of scope to vary my route. As I am doing it day in day out and in all weathers, I would rather do it on something I can enjoy riding and for it to be a daily pleasure rather than something utilitarian and boring.
As stated previously, I don't need panniers, don't like mudguards and at most I will run with 25mm rubber so this obviously frees up much more choice... and I am fortunate in that it doesn't get left in a communal bike rack as it will have a nice warm office to sit in during the day and will never get left locked up anywhere.
I also take the point about component wear rates. But to be fair, my bikes are always well maintained and wear is kept to a minimum (My MTB has had the same Deore groupset for over 5 years and it gets ridden
hard in all conditions) and having to replace a chain, cassette etc every 6 months hardly compares to the cost of running and maintaining a car over the same distance and time period, so again not an issue.
I don't really have any experience of Carbon as a bike material beyond the Carbon fork on the Triban, I figured that as they make all sorts of things it would probably be ok but you hear and read a lot of differing opinions on it and in particular its durability... and I gather that as with traditional materials, all Carbon frames will not be created equally and will be of differing quality.
I will expect this bike to last for a good few years to come so my priority will be the frame / forks with the spec of the components a secondary consideration for now.
The CAAD 10 does look very nice indeed. I think Ultegra will be overkill though and I would be tempted by the 105 spec and spend the change on some other bits.