You're highly susceptible to suggestion. Find some benchmarks were you can properly measure latency and you'll be disappointed.
No, I'm highly susceptible to my own experience. I've used vanilla and patched kernels interchangeably and noticed a big difference in responsiveness under (particularly heavy combined cpu/io) load. And even if it's kernel is in an infant state compared to Linux, Haiku performs better (in responsiveness) during equivalent load on my machines (core i5, amd x2, p4). And for a desktop OS, I always want responsiveness to take priority over throughput, I don't care if a file takes X seconds longer to copy as long as it's done without me noticing any degradation in responsiveness. If I'm running a server then that's a totally different thing of course.