Tried my share of graphite iron shafts, YMMV...
Smoothest: Roddio (hands down)
Best flighted: Steelfiber i95
Plays way too stiff for my old guy swing: Crazy CBI-02 Evolution, Fubuki AX i425
Good but not great: Quadra 100i, Tour AD 75, Recoil, OTi, MMT, MCI, Honma Vizard