I don't believe tethering is free through the hotspot app. The superuser app being there does not mean you have superuser it just means the app is still there. Easiest way to find out is install terminal from the market. Once it install start it and type in SU, if it says access denied you don't have root.
With that being said, if you did the update either OTA or manually through the update.zip method you do not have root. unRevoked 3.1 does not root 2.1 but they said on their twitter yesterday that 3.2 was coming along and would root and install s-off on Froyo across the board. So either wait or do it the hard way!