i've tried the adhoc using my Magic and it does work pretty fine. The only problem i face is that with the Adhoc setting in place, normal infrastructure WiFi scanning and connection acts a bit slow and weird. But I do rely on this Adhoc mode heavily as i don't have data plan

So in order to satisfy both situation (Adhoc and Infra),i have actually created some scripts to enable me to switch to Infra (normal) or Adhoc on the fly via GScript on the phone(root required) itself without the need of ADB.

If u guys want it, i can share it out but for it to work there are 2 conditions,
1) U know how to set up ICS on your pc
2) You will have to edit the the Adhoc name to the name you configured in 2 files

cheers