As was to be expected and confirmed in the Google Webfonts FAQ, even the fastest method (hosted Google Fonts) is 0,26s slower then the version without web fonts. Locally hosted fonts are marginally slower, but that’s because (for reasons I don’t fully understand) 2 font-files were loaded instead of only 1 in the Google Fonts-powered page. Cufon isn’t really worth mentioning here, it’s dead-slow and has become rather irrelevant I guess. I did not test a version with images instead of web fonts, but that would probably yield approximately the same result (5 image files, each somewhere between 4 and 8Kb?) and is sub-optimal form a SEO and accessibility point of view.
So 0,3 seconds, that’s not too bad, no? Or is it? If you’re creating an online shop, Amazon’s experience might be of particular interest here; every 100ms delay costs them 1% in sales. So are you willing to lose 3% revenue just to have those nice fonts, which your visitors probably couldn’t care about less?
My advice; don’t use web fonts if you value performance. And you should consider performance a top priority, not just for sales’ sake, but because raw website performance also impacts usability and search engine ranking.
If your brand identity manager insists on using the right fonts, performance be damned, then try to at least follow these basic best practices:
have the CSS that defines your fonts (with font-face) as early in your HTML as possible and certainly before any script is loaded
use Google’s hosted font-solution if possible; it’s fast, the CSS is optimized for the browser that requests it and there’s a lot of free fonts at your disposal
if you have to host the fonts yourself, make sure to serve the WOFF format (the new standard) and SVG (for iPhone/iPad) next to the more traditional TTF (the “old” standard) and EOT (for MSIE)
if you’re hosting your own fonts, configure your webserver to on-the-fly compress ttf, svg & eot-files (woff-files are already compressed) and set expire-headers for all fonts in the far future to allow optimal caching (example for Apache):