Even though it's a point release, the latest Amarok comes with some major new features and all the benefits of the 2.2.0 release. Dubbed Weightless, the 2.2.1 release is full of bug fixes and polishing from 2.2.0 release as well as improvements to music management, podcasts, and the ability to update Amarok scripts.
Amarok is already speedy when processing large media collections, but this release includes a tweak to take it up a notch. In the past, Amarok would scan an entire directory -- including sub-folders -- when the main directory had changed. Now Amarok can just breeze through the main directory if the subdirectories haven't been modified, making it even faster. And it's plenty fast already: I've passed a 57GB collection through Amarok in just a few minutes.