The good news is so far the local adjustments are proving extremely useable. I have been testing a lot of creative local adjustments and ways of going about doing things given the combination of tools Aperture has available for my upcoming Adjustment eBook.
The bad news in case you were wondering is that even though you can save brush adjustments as a preset they are only useful on images of the same dimensions - there appears to be no way to make them "relative" they are absolute - so… the utility of a "creative border treatment preset" as described in the Aperture marketing literature seems to be not so practical in the real world of multi-cameras and crops.
As this is early in the Aperture 3 release cycle this could be wrong - considering that a friend of mine has been able to provoke the book tool to provide font transparency that not even he can reproduce consistently but I have seen it with my own eyes. We have a side bet that when this "get's fixed" that it either works all the way or goes completely away - I am taking the it goes away stance.