Wu Fengguang and KOSAKI Motohiro have published patches this week that they believe will address some of these responsiveness issues, for which they call the "system goes unresponsive under memory pressure and lots of dirty / writeback pages" bug. Andreas Mohr, one of the users that has reported this problem to the LKML and tested the two patches that are applied against the kernel's vmscan reported success. Andreas' problem was the system becoming fully unresponsive (and switching to a VT took 20+ seconds) when making an EXT4 file-system when a solid-state drive was connected via USB 1.1. On his system when writing 300M from the /dev/zero file the problem was even worse.
The patches from Fengguang and Motohiro can be found in this Linux kernel mailing list thread. With the Linux 2.6.36 kernel merge window about to be opened, let's hope these patches work their way in there during this next cycle, but for those planning to run the stock kernel on Ubuntu 10.10 and other Q3'2010 distributions, it is already too late unless these small patches end up being back-ported.