the US carbon was my real favorite in 2012 and for sure will be for light wind conditions in 2013. Used it with NP Hellcat 7,7 and a 52 DRAKE and with NP H2 9,2 with the 58 DRAKE stockfin. With both sails it is a really amazing combo, easy to use, fast also in direct comparison to other more conventional large boards like 145 sharks or big futuras. Moreover the US has a much lighter and more sporty feel compared to the latter ones.
The best sensation of course is the planing capability in very very light winds and the capability to plane through lulls. This I valued particularly when sailing with 7,7 in changing conditions. All in all the US for me was a very good choice which might be even supplemented with a 10+ sail this year to even further lowering the hurdle to plane.
Don't expect big advantages from the slight change in shape of the 2013 model, so I would go for the 2012 US in carbon if you can get one.