I tried to check by saving a page locally via Firefox - it was over 400K, and a 2nd page I visited and saved was over 600K all up. That's 1mb for 2 views. That would cost me $2.04 if I visited from my mobile and was paying casual data rates! I know there is caching and stuff for js and css, assuming that IE under Windows Mobile 6.5 fully supports such, but it still seems big - those figures would probably stand for the first visit to a xenforo site.
I'd like to know how to more accurately measure this if anyone has some ideas.
This should also all be kept in mind when developing a mobile style - it's not just appearance, but bandwidth requirements also that needs to be taken into account.