I have a One Plus One (thanks Mark). I bought it for my mum but she said the size was "a bit ridiculous" and now I have it.

In general it is super nice. Battery life is epic, camera is pretty decent, screen is great and it is 'snappy' as you would expect. Though to be honest the speed improvement over my 3 year old Tegra 3 HTC One X running Cyanogenmod 11 rarely makes a real world difference to me right now. I don't understand why scrolling webpages in Chrome is not always smooth.

I really feel that it is a borderline acceptable size, and a lot of what makes it usable is the texture on the back. With one hand I can unlock it, swipe short messages and just about reach the notification shade at the top of the screen.

The Nexus 6 is a bit wider and that will make it a strictly two handed affair which is bit inconvenient. It would also be even more annoying to fit into my jeans. Also, is it really twice the price? Meh.