Tempted by Nest, but have some niggles stopping me from ordering.
My last house has a Honeywell CMT927, which worked pretty well, as we have a relatively fixed schedule (but not rigid for all days). Just moved house, and the boiler here does not have a thermostat... just on/off at set times using the digital control on the front of the boiler. Therefore I was going to get another CMT927 for full on/off control and wireless thermostat.
Nest looks very interesting, but I need to justify the price difference over the CMT927, including the extra functions that Nest offers. Nest has learning, auto-away and wifi; however, CMT927 cost £120 new or £75 from auction site... compared to £179 for Nest.
I really like the idea of the Evohome: the Base Pack (main controller, stand and relay) is on sale for around £190, which is reasonable compared to Nest; but my house has lots of rooms/radiators, and we would need at least 6 (if not 8) radiator controllers... at £60 each, that's £360+ on radiator controls!

I can see that becoming a £600+ install.
One thing really putting me off Nest is that you have a modern, good looking thermostat/gadget fixed to your wall, with an exposed power cord dangling down with a plug at the end that is simply plugged into a wall socket!!! I don't know if the free install options includes hidden wiring if it is not already there from your previous thermostat.
I'm thinking to spend £75 on a CMT927 now, and see what options there are in 3-5 years.
Thoughts, anyone?