Over on xda, there is a thread on using root to replace a wpa_supplicant file in /system/bin. Now I can "see" ad hoc and connect.
I can disable mobile networks and still get an internet connectoon from my rooted eris. It is running the rooted wireless teather app. Speedtest.net shows im still getting good speeds. Now I can drop the vzw $20 plan.
This tab really is great, no complaints!