I just had a horrible thought:

For months now I've been using the new MS fonts in my emails - the body text is in Calibri (the default for Outlook 2007), and I use of smattering of Consolas in my signature to space out phone numbers and other contact details neatly. I think it looks pretty good, very modern, very clean.

BUT - what if the recipients don't have these fonts installed on their system?  How does it degrade?  Will they see a sensible alternative, such as Arial or Verdana, or will it just render in *shudder* Times New Roman!?  People will think I have no taste!  That would be nearly as bad as those folk who insist on sending business emails in 16-point fuschia Comic Sans MS!