It is looking increasing like the proposed .webfont file format for embeddable/downloadable fonts will be the standard, and will be supported in CSS3.
Safari and Firefox support using TrueType and OpenType fonts, however the licensing restrictions on most fonts, in particular all the good fonts from the major type foundries, prohibits use in this fashion. There are workarounds, such as sIFR, however this opens up a whole new can of worms such as the use of Flash.
I, for one, would love to forego the use of images for my website masthead and have proper, browser-rendered text. This would improve accessibility, potentially reduce the amount of data required to be downloaded by the browser to display the page and assist with search engine recognition.