I run a 52, 39, 26 in front, I run the 10spd Ultegra front deraileur and a Long Cage Shimano LX rear deraileur old style with the adjustable cable barrel built into it ( I just like this set up better ) I have also run the new style XT Long Cage rear deraileur as well with no problems but there seems to be a little more cable angle (sharper) at the cable connection at the deraileur on the new style XT & XTR Units, they seem a little more finicky to adjust & need a inline cable adjuster installed on them due to the lack of the built in barrel adjuster but they work fine. All shifts well up front but I would never go smaller than a 26 tooth here as that would be pushing the limits of the front deraileur to far and not lift the chain to the middle ring properly. I also use a Jump Stop Chain Over throw protector and adjust everything to tight tolerences to make sure there are no chain over throw issues either way up front.

Take Care,
Bill G