Just checked, the shimano clutch rear mechs are not 10 speed specific and thus this new rear mech tech is not a benefit of 10 speed. You can stick with 9 speed and have the advantage of clutch rear mech.
Complete bollocks I'm afraid. Shimano being the greedy barstewards they are changed the cable pull ratio so that the clutch mech only works with the 10 speed shifters. Apparently it is possible to shim out the cable clamp on a 10spd sram mech so it "works" with 9 spd shimano shifter, but it seems a bit hit or miss. My drivetrain is getting worn out anyway, so the only extra expense is the shifters and rear mech which with a bit of shopping arround came to £120. My old 9 spd xt kit will replace the deore mech and thumbshifters on the fat bike. Those microshift should fetch decent money on the fat bike site which will recoup a bit.
'97 GT STS 2 - XTR'd to the hilt.
'94 Retrodale Delta V