Right, so just for a change, this isn't a "what bike should I buy" thread, it's a "this is the bike I bought and my thoughts on the alternative candidates".
For contaxt, my current bike is a generic carbon frame bought from Graham Weigh in North Wales. It has a mix of SRAM Apex and Rival, Omega Mach 1 or Mavic Kysrium Equipe Wheels (depending on the time of year), Speedplays and a Fizik Aliante. I ride with the local club and enter the odd sportive and time trial.
I've secured a contract working close to home, so have bought a rack and pannier for commuting on that, and set out to buy myself something a bit nicer for the weekend. Stiffness, handling, still a bit of comfort, confidence-inspiring on the descents, and affordable (see my other thread on impending twins!).
It's worth saying that I've ridden very few bikes, so when you read in reviews that a bike 'stiff at the BB' or handles slightly differently to another bike, I was unconvinced as to how much I would feel these differences. So anyway:
Kovert FX Race £1200-ish - full carbon with Ultegra and Ksyrium Equipes.
Good spec on paper. Better ride than the Graham Weigh (hereafter referred to as GW), but like the GW, didn't feel that responsive to pedalling input. Seems to need wrestling side-to-side if you get out of the saddle, like you're wringing the power out of it.
Cannondale CAAD8 - Alu, 105.
Wanted to find out what the fuss was about re the differences in frame material. Put a smile on my face straight away, and had me straight into the drops and chasing a car down the road like a daft dog that's escaped from the garden. However, a fairly harsh ride, and I could see how I might feel a bit beat up after 60 miles. If I was a crit racer, I'd be all over this.
Giant TCR Composite - carbon, part Ultegra, reduced to £1500.
Not a bad compromise, stiffer than the covert, but didn't feel like I could 'light it up' in the way that the CAAD did.
All the following bikes were at a 20% discount.
Cervelo S2 - carbon aero frame, Ultegra, Ksyrium Equipes, £2000
Ey up, this is quick. Stiff and responsive, but you feel the bumps as per the CAAD. Also, I got the feeling it would be twitchy at high speed. The second half of my little test route included a nice fast section with a very gentle downwards incline. On the drops and giving it the beans, I could already feel it, not twitching, but communicating a LOT of info and made me think that I'd be wary of doing 35mph+. It struck me that this is for a ballsy, experienced rider with better handling skills than me.
Cannondale Super Six 105, £1400-ish
Surprisingly similar to the CAAD, nice and quick but you feel the bumps.
Trek Madone 4.9 - Trek's traditional 'Pro' frameset, Di2, Bontrager kit £2080
With a 20% discount off the RRP for the 2013 model, I couldn't not give Di2 a go. However, if I'm honest, I was a little bit 'meh'. Don't get me wrong, instant shifting and all that, and the front mech auto-trim is something else, but the differences were sufficiently small that the £400 premium and uglier paint job than the 4.5 were deal-breakers.
However, the frame was awesome. Stiff, light, willing to accelerate, and just takes the edge off the bumps. Couldn't call it 'comfy', but I guess that's what the Domane is for.
Trek Madone 5.2 - Aero frame, Ultegra, Bontrager, £2,300
Lovely bike, but the frame properties didn't seem any different from the 4 series. Biggest difference was that nice Ultegra chainset, really solid.
Trek Madone 4.5 - Trek's traditional 'Pro' frameset, mix of Ultegra and 105, Bontrager kit, £1600.
Awesome frame as above, nicer looking than the others in the 4 series. Cheaper chainset, but that just means that my christmas present is already known. I don't mind the same paintjob as the pro bikes so long as there aren't any sponsor logos, so this hits the spot.
Trek 4.5 it is then. THIS IS THE BIKE I BOUGHT! (just to clarify for those who I'd confused - sorry!)
Also of note is that I'm always told that people buy bikes with their hearts. I didn't, otherwise I'd have been lured by the Cervelo, the Colnago that I didn't get to try, or gone for the Madone 4 on project one with a snazzy paintjob. The brand is a bit corporate, but the geometry is just right, and the frame characteristics are lush. I bought this with my head- mostly.