I did a bit of research on this last night as I was getting a bit confused.
Metal = Sintered = high heat generation / long life
Semi-metallic = Organic = short(ish) life, but low heat generation
Metal are not recommended for DH, which is why JD might have been struggling yesterday with pump up, but I didnt really equate yesterday's riding to heavy braking / DH type conditions...... Hmmmm maybe JD has the ghost of Kev in his system again?!
This is a useful summary:
http://www.fibrax.com/moreinfo.php?cat=12I, however, have metal/sintered on mine and they seem to be OK (they do say that can make a difference whose pads you use - I have just ordered one set of fibrax sintered to try from CRC). We will see - got to be better than the 1mm of pad I have left at the moment!!!!
Any other make a supposed to be better than shimano (and cheaper) so I will see. After ordering it looks like EBC might have been the best, but I will see how I get on.....