I wrote an article a while back on font replacement techniques, this is a quick update about Google’s version of this which is seriously easy to use.
The Google Font API allows you to use any font from their font directory or you can use the font loader to load other fonts which they co-developed with TypeKit.
Using the Google Font API
There’s no point in re-inventing the wheel so I’ll just link to a great article and video guide by Jeffrey Way over at Nettuts. You can have a look at his article here.
Other Info
The great thing about the Google Fonts API is the fact that you can still use CSS3 effects on your text if you want to. As for page performance, obviously the initial download may slow your page down slightly but they do try to cache everything to minimise and extra loading times, just make sure you don’t try and load too many fonts!