Aperture 2.1 Sluggish Exposure Adjustment Sliders

Question

Description of Problem:
1. When the Straighten Brick is applied to an image being adjusted, the Exposure Brick sliders become erratic and do not track mouse movement or the Wacom Tablet Stylus tip.
2. This condition substantially worsens when the Highlights and Shadows Brick sliders are also applied to the image simultaneously.
3. A similar condition appears with the combination of Crop and Highlights and Shadows.
4. This condition is so severe that I took my Mac Pro 2 x 2.66 GHz Dual-Core Intel Xeon with 4 Gig's of Apple Ram and NVIDIA GeForce 7300 GT 256 Vram Computer to the Apple Store Genius Bar for diagnosis and possible repair.
5. After my having demonstrated the problem, the Genius Team took my set of internal hard drives out of my computer and installed them in a brand new Mac Pro in the Apple Store, where the problem persisted, thus eliminating my hardware as part of the the problem.
6. It was then suggested to me by the Genius Team that I create a new Aperture Library, trash my Aperture Preferences and re-import my images into the new Library. The sluggish and erratic Exposure sliders problem persisted!
7. I then, on my own, created a third Aperture Library and imported only a few images. As long as the Straighten Brick is not part of the adjustment pallet, the Exposure Brick sliders behave normally, tracking the mouse or Wacom Tablet Stylus Pen tip.
However, when the Crop and or Straighten Bricks are added or combined with the Highlights and Shadows Brick sliders, the Exposure and White Balance sliders become erratic, sluggish and nearly useless.
Of note, the Enhance sliders, however, are unaffected by the above combination of Adjustment Bricks.
8. I then tested this scenario on both the 2 x 2.8GHz Quad-Core Intel Xeon and 2 x 3.2GHz Quad-Core Intel Xeon Mac Pro models in the Apple Store, with extremely similar results. The later, 3.2 GHz Mac Pro with the NVIDIA GeForce 8800 GT 512MB Video card installed and having 4 Gigs of Ram.
9. I tested the scenario with my images as well as with the the sample images installed within the Aperture Application Library, both with identical results.
10. Clearly, this phenomena is a defect in the Aperture Software, as it can easily be demonstrated independently of specific Apple hardware, and as it is very common to apply the Straighten, Crop, Highlights and Shadows adjustments to an image, renders the Aperture Application useless, as an effective workflow solution. A Professional Photographer cannot guess at the Exposure settings and or wait and hope for the adjustment slider to track mouse movement while it jumps around erratically in the process.

Answer 1

What you're doing simply requires more calculations than your processor can perform in an acceptable amount of time. The tradeoff of the non-destructive image editor is that every transformation you apply has to be recalculated and effectively re-applied every single time you make any change to any one of them on the stack. Given the average size of a modern camera raw file, this gets very expensive very quickly.
There are certainly ways of caching intermediate data in the interest of drawing speed, but the white balance and exposure sliders fundamentally change every aspect of the image data's interpretation and are some of the most expensive operations you can possibly perform. Not only does it have to loop through every single pixel in the image to calculate the various gamma encodings you ask it to with every little nudge of the slider, but it also has to rotate them all by however much you've asked the straighten tool to. Top that off with the fact that Aperture has never been widely regarded as a "speed demon" and you've got laggy sliders.
Try Lightroom. You'll probably find it lags at times, too.
Now try sharpening a 1MB file in Photoshop 2 running on a Quadra. Not so long ago we had to wait hours for every single trivial adjustment to our low res and completely unprintable images to complete only to discover that it wasn't what we wanted at all. This wasn't a defect, it was the result of pushing the available technology beyond its limits. I have no doubt that Aperture could and should be optimized significantly, but the fact of the matter is that artists will always find ways to saturate the bandwidth of any computer on the market, however powerful.