one thing you should wonder, do you think is good enough to leave a image to represent a heading? you might think, oh cool that look nice, but remember it affects SEO, there is another solutions for this workaround (cufon) but is not as flexible as webfonts, i think that webfonts will never replace a system font, but the web designers need to get a fallback, a reliable fallback.
Answering your question, i think is not possible to get the benefits from a webfont, but one possible solution for your problem related to the downsides is to ask the visitor to install the font required, but it would be not practical.
one thing you should wonder, do you think is good enough to leave a image to represent a heading? you might think, oh cool that look nice, but remember it affects SEO, there is another solutions for this workaround (cufon) but is not as flexible as webfonts, i think that webfonts will never replace a system font, but the web designers need to get a fallback, a reliable fallback.
Answering your question, i think is not possible to get the benefits from a webfont, but one possible solution for your problem related to the downsides is to ask the visitor to install the font required, but it would be not practical.