2.3.15 benchmarks (quadrant) about the same as 2.2.20, but it feels somewhat faster/smoother. Could be all in my head...
The leaked update is deodexed, that's probably the speed increase. I deodexed my system using Motoboy's method in the hacks section and I noticed an instant jump in speed/smooth scrolling. I THINK it has something to do with changing the way memory is allocated but I just did it to modify my system files. Because of that tweaking I've already done though I'm afraid to try this update without reverting. Likewise, I am afraid that if I revert to do so I won't notice any real gains. If it's just bug fixes than it's not worth it, I rarely run into them.