Agreed, for me also the main reason to root was to get the WiFi tethering without having to pay an extra $30/month for something I use only sporadically.
The no-root tethering programs (EasyTether, PdaNet) only work on USB and/or Bluetooth, and in my experiences worked very poorly when they worked at all. Sometimes I had to do multiple resets / uninstall & reinstall / redo settings to get it to work then the connections would drop after a few minutes, etc. Totally unsatisfactory.
WiFi seems to be a much more reliable standard for internet access but requires rooting (I don't know the technical reasons why). I found that the Wireless Tether app would work only on 4G but not 3G, whereas the unlocked hotspot that comes with some custom roms would work only on 3G. Grrrrr....
Anyway I FINALLY got the Wireless Tether working on 3G as well as 4G when I did the following. I gave WiFi Tether some tough love... While I had uninstalled and re-installed every version of Wireless Tether many times with no joy, one time I tried clearing data (via Menu / Settings / Applications / Manage applications / WiFi Tether / Clear data) BEFORE uninstalling WiFi Tether. Then after re-installing, it worked on 3G AND 4G... After that I could switch 4G on and off multiple times and it all worked. That was a couple of weeks ago and while sometimes I lose the connection and I have to stop/restart Wireless Tethering once or twice to get the connection working again, it's not a major inconvenience.