EBBs also allow you to change your crank position which tweaks geometry and fit. it's a pretty good system if it works well.

trouble is taking hits on downhill bikes with an EBB. that is the one part of the bike that should be strongest and well... adding moving parts that you have to set in can get problematic.

JT - basically an EBB is a bottom bracket shell that operates like a cam, so the spindle of the BB can be moved in a small circle inside the BB shell. it allows you to move your crank in relation to everything else on the frame, including the rear axle.

for discs, sliding dropouts. definitely where its at.