I do like the look of it, oh yes indeed. It seems like I can use my 305 heart strap and cadence sensors too, so that could mean I only have to buy the unit itself rather than the more expensive 'performance' bundle. Looks like the Ant+ allows you to connect up to a set of scales too, so the 800 can record your weight and body fat % too. How cool is that!
I'd want to explore map options too. I am a little concerned about the 1yr warranty though. For kit that expensive, I'd like to see more than that.
I'm on my 2nd 305, the 1st one stopped acquiring satellites after 18 months and was replaced under the 'out of warranty refurb' scheme. Okay, it's cool Garmin offer that service but it doesn't make me feel confident that my £450 bit of kit wont want replacing within a couple of years.... but I guess that's a risk you take with every purchase!