Well, wouldn't you know it, this patch http://lists.infradead.org/pipermail/libertas-dev/2009-May/002412.html seems to fix the Z2 WIFI driver timeout / failure issues.
Thanks to GPSFan for spotting this.
Now I can stay connected to my AP for hours. Great Success!
In other news, the battery driver is in, along with LED triggers and some other nice bits.
I should have a new kernel and userland up in a short while.
Oh, and if you haven't already, check out the wiki on OpenZipit I've added some info.