**WARNING**
I installed the ICS fix cab so that I could tether (Phone as Modem) without being charged... on a whim, after resetting the device, I went into the registry to confirm that the settings were implemented.
I found that the "Extension" key was still set to "isext.dll" and the Force Cell connection key was still set to "Phone as Modem".
After changing the registry value, the "Phone as Modem" keeps coming back. There is a thread about this here:
http://forum.ppcgeeks.com/showthread.php?t=83797
But I thought I'd warn everyone in case you install the cab and think it's going to work.