I can confirm that disabling power-saving reduces latency from 50ms -> 5ms but it increases the battery drain drastically. There are several WLAN bugfixes in the PR1.2 patches which might have caused the higher latency. the IPv6 support and the 2.6.28.10 patches could be alternative causes but I suspect its the PR1.2 fixes. I'll do a test with a kernel w/o the those fixes.