I bought the middleburn x-type Duo cranks recently for my sram 10 speed set up. Works perfectly, just take time in setting up the gears and the shifts up front are sweet, plus I’m no pro racer so not worried by speed of shift as only talking 100ths of a second! main concern is that it actually changes gear.
Also the new duo which I have mounts on a 4 arm spider so to make the replacement rings cheaper as before the inner duo ring was the spider so was costing around £80! not any more. Buy them from RJC Xtreme as will only cost you £205 as you get a £20 discount for items over £100 I think. Here is the link to save you time:
http://www.rjcx-treme.co.uk/acatalog/RS-8_X_TYPE_DUO_CRANKSET.html
Great cranks and British with a life time warranty, can’t go wrong..