I've been using the [presto plugin for yum](http://fedoraproject.org/wiki/Releases/FeaturePresto) for a while now (a year? can't remember) but only now it is being pushed as a "cool new feature". Did I miss something here?
Presto allows you to download only the deltas of updated RPM packages, which makes the updates' size decrease a lot and, by consequence, speeds up the updating process. I guess it reached stable status recently and I wasn't paying close attention :(
**UPDATE:** So the changes are not actually on how the plugin works, but actually on [how it accomplishes its tasks](http://kad.blegh.net/index.php/blog/show/People-keep-talking-about-it....html#comment574). Now this is new :)