I had downloaded it early this morning and have been playing around with it a bit. Have to say that this really works. The ability to brush in changes locally is very nice. The even more interesting feature for some, is that the plug-in architecture could allow other developers to incorporate their RAW processors as plug-ins in Aperture. (None yet, but the platform now exists.) What this means is that one could load and manage images in Aperture, and if they wanted, could invoke some future C1 or RAW Developer, or even ACR conversion of the RAW file, and not just use Aperture's own algorithm and tools. This does not yet exist, but the potential is now there. This is very cool stuff for Apple and Aperture.
I am waiting to see the Nik Software Viveza plug-in, as well as the PictureCode Noise Ninja plug-ins that are now in development. This could finally usher in the plan of having a single app, Aperture, be able to accommodate digital asset management, RAW conversion(s) via several options, full adjustment palettes, complete variety of output options (Web, books, prints, etc.), and other things not yet released. Doing it all from one place, without having to shell out to other apps and trip back in. This is really great stuff.
LJ
P.S. Needless to say.....this is starting to look like head-to-head competition with Adobe PS. Some of the changes/adjustments will be "permanent" as in pixel changing things like PS, but others that are instruction sets for the RAW file will remain. There is also the ability to possibly create multiple version adjustments inside as well as still going outside to external editors as you can now, but doing it all inside, and still having control over the RAW adjustments. This is way cool development.