If you are in the market for something with a little more comfort than a brick-hard race machine, but don't want to sacrifice much, if anything, in the way of performance, then you may just have come to the right place.
Cannondale deliberately build some 'give' into their Synapse frame and fork, calling it Save Plus suspension, aiming to reduce the trail buzz and fatigue this can induce over long days in the saddle. This is done by strategically shaping the tubes and altering the lay of the carbon in these areas to allow flex in the right direction, staying stiff where power delivery needs it. The result is a bike aimed squarely at the endurance market, for those riders that disappear for whole days and regularly knock off three figured rides. The ability to accommodate up to 32mm tyres helps with the comfort too, making this a great all rounder. All reports are that it not only reduces road buzz significantly, but retains more than enough stiffness for sprinting and efficient power transfer - truly the best of both worlds.
This 105 option is a great starting point with a well tried and tested Shimano 105 groupset, packaged up with capable Mavic Aksium WTS wheels and Cannondale's own finishing kit. If you like the frame it might be worth stretching another £600 for the disc model, just to get that extra confidence and control at speed.