I'm not sure if that matters too much - it takes over a second for those to load on my (broadband) connection. That means the page first renders with standard fonts, then snaps into the fancy downloaded ones a second after load. It feels horrible.
Edit: I tried it with Firefox and it does indeed use the default font until the new one is downloaded. The transition is not nice but better than nothing.
In any case, to me it's just really more fluff, and not likely to be really usable for a long time to come...just like things like rounded corners in CSS are fun, but a narrow solution when you have to support IE6...and yes, a lot of us still HAVE to support it. I won't turn down a job just because they have that requirement, just have to adjust my expectations.