Thanks highlandsun. I did a little bit of testing on Linux at home, but had some issues with adb - hopefully I'll get that working tonight to really test it. I'm sure it does work now tho, as the icon is now showing up correctly in the notification bar.
Let me know what you find on Windoze. Might be good to note, according to
http://www.android.com/tether, if you're running WinXP it either must be SP3, or you need a hotfix for SP2 to fix the RNDIS drivers. It's in the comments, Google makes no mention of it in their USB tethering how-to. Obviously that's for native devices...