Why is USB not an option? Its always my preferred choice as that way you aren't draining the N900s battery when tethered, only your laptops.

The only question then is what uses more, your WiFi chip (which you can then turn off if using USB) or charging the N900 - mostly depends if the N900 is already fully charged I guess.

Although my preferred is probably JoikuSpot with the N900 plugged into USB or the charger. (assuming the full JoikuSpot works, I couldn't get the Beta to work for me)