I got my net4521 a few days ago, and after borrowing a CF card ('cause I stupidly forgot to get one of my own), I had it up and running Pebble Linux (from Tor Amundson) in no time. A few days later the CM9, miniPCI 802.11a/b/g card, arrived.
I've been poking at getting the 802.11 card up-and-running, and met with some success. Right now a kind soul is helping me learn how to use buildroot to build a Linux from the ground up for use on this box. We'll see how that goes, and I'll try to post the steps here.