Well had a few minutes to play around and this is probably the most ridiculous phone I'll ever own. I always felt room to upsize with my Note 2 but I think this really is the limit (Not in a bad way, in a 'I think I've finally found it' way).
The build quality/feel is just obscenely good, no other way to describe it. If Microsoft are going to carry on in the same vein (and their surface line suggests they will, quality wise at least), they may get more of my money in future.
Have popped 8.1 onto it so will just have to put it through it's paces as far as usability is concerned. Hopefully there won't be too much missing coming from my Note 2. The general system wide fluidity is wonderful too, as are live tiles.