SPD's on everything for me (most of the time).
I don't understand all this pish about not being able to clip out when it all goes wrong? It's easy... it just happens... I don't even think about it. I've been trapped by the bike a few times... but I'm usually trapped by my laughter. I love stacking
Having said that I use SPD's all the time I took a winter out off from them a couple of years ago and used flatties. As an ex BMXer I had no problems on DH's or jumps etc but really steep/lose/slippery climbs where you need to pull up as well as push down were almost impossible. It became very frustrating as I was never as good with the flatties as I am with SPD's.
For performance SPD's rule.
In the pre-SPD days I used to have my toeclips up so tight that any stack had serious pottential - SPD's were a godsend!
Pedalling style is important - I spent ages learning to pedal in circles pulling up and pushing down - I still practice this on flat sections and I believe it helps. I'm also a spinner - I like my gears low and my leg speed fast.
He's not the messiah, he's a very naughty boy.
95 Kona Explosif Singlespeed/Fixie - 100% Thrashed since new and it's still very well loved (and it looks it).
Dave Lloyd C.A.T.S W.I.S.K.A.S - Built, ridden, loved, and sold.