well I went to pick one up last night, it was between
TomTom One V2 - £149.97
TomTom One XL - £179.97
reading the back of the box they both seemed to be identical, I plumped for the V3 in the end as it was so thin and light, easy to chuck in your pocket.
Got it home and it all seemed fine, until I tried to conenct it to TomTom Traffic. It flashed up with a message saying I needed to attach it to a RDS adaptor, couldnt believe it, looked on the website and these things are £70

plus you have to have some daft lead comin gout of the unit.
Looking at the tech specs it only says TomTom plus compatable, no mention of this only being with adaptor, cant believe it doesnt have a bluetooth connector. I have checked online and it seems the XL does have bluetooth 2.0 in the specs, so I am going to go back today and swap it for that model.
Other then that its really great, so much lighter then my old unit, nice screen, very quick to work out routes and its all pre programmed with speed cameras etc right out the box.
edit - just come back with TomTom One XL, much bigger screen and the maps come on a memory card instead of built in. and it has bluetooth built in.
all in all well worth the extra £30 over the V3