Good morning! Apple has just released the next major revision of OS X, Lion, only through the App Store.
Should you upgrade? Not unless you want to experiment on a spare machine or partition that you don't need for audio work for a while. The two main DAWs on OS X, Live and Logic, each have some issues with Lion. There is a good short article about that here.
As the major DAWs come into sync with the new OS, I'll test those releases with Aalto, and keep you posted.