I wouldn't be surprised if they made a hardware counter to tethering because of the legacy iPhone. That would make it hard to distribute.
So far Windows Mobile is the best tetherer through WiFi. That's an option.
Windows Mobile devices can tether via WiFi with an app (WMWiFiRouter) that makes the phone a "mobile hotspot" and you can even put WEP, WPA on it, etc. or just leave it open for the public. But Windows has this thing called "Internet Connection Sharing" built into the OS. The funny thing about this is that you don't even need a tethering plan because it just uses the data plan. heh