Just fyi (I am using Mimicry actually, but the problem seemed common to this as well when I used to use it, so posting here), the random slowdowns that kinda appear to be related to multitasking on ICS roms such as this seem to correspond with emmc-qd (I assume the kernel module responsible for onboard flash IO) using up a lot of CPU. This is with and without a swap partition on my SD card enabled. As previously stated in both threads, turning max background procs down to 2 makes the problem far less common, but then I start losing half written messages when I'm checking something in Opera, etc..
I'm actually switching to cm7 now as it's getting too much to live with, but maybe this is helpful for a dev to look at? I've tried mucking with different IO schedulers to not much avail (SIO by default).