Looks like Windows Phone 7 Mango will be getting a mobile hotspot feature.
The full details can be found at http://arstechnica.com/microsoft/news/2011/08/windows-phone-mangos-wi-fi-hotspot-secret.ars
I for one am looking forward to that. I can use it to quickly get online with my laptop when no WiFi is available. I have an android device (Samsung 551) that can do hotspot as well, but my Samsung Focus is my main device and its a pain having to SIM swap.