Excellent explanation; didnt even know there was such a thing as 'infrastructure' mode. This probably explains the change being made to wpa_suppliant to have the device support ad-hoc. Lovely explanation on the wiki page.
Btw this seems to be an issue with honeycomb not the transformer:
http://forum.xda-developers.com/archive/index.php/t-1059245.html
"This is true, and I was able to get it to tether by upgrading and using infrastructure mode, but I believe there are many things such as some corporate networks that use Adhoc.
I seriously doubt that many corporate networks are using adhoc Wifi networks!
Out of the box, Android doesn't support adhoc networks, but it can usually be enabled by editing the wpa_supplicant.conf file on rooted devices."
So that was exactly the change being made to wpa_supplicant; and now I understand.
It's probably because Asus Eee pad needs infrastructure mode instead of ad hoc. The wireless tether apps you used only creates ad hoc network. That's ok for most devices but some devices and pretty much all corporate devices require infrastructure mode. I'm wondering if all Honeycomb tablets need infrastructure mode to connect.
Very few phones will do infrastructure mode. My Galaxy S phone has built-in Mobile AP program that does true infrastructure mode. I can wireless connect any WiFi device to it. You're just going to have to use the Bluetooth method til you get a phone that can do infrastructure network.