Some people have asked why Lightroom 2 seems to have slowed down so much after the recent software update. The answer is pretty simple. Adobe has improved their algorithms for Lightroom 3 (don’t ask when it will be released, I don’t know). They have now provided some of these features in LR2.

Here are the release notes from Adobe’s website:
– Camera Raw 5.7 includes an updated demosaic algorithm designed to provide compatibility with settings applied in Lightroom 3 beta 2.
– Lightroom 2.7 also includes the same updated demosaic algorithm. The updated demosaic algorithm will appear as a subtle shift in noise characteristics at default values.
– By default Camera Raw will display the image adjustments exactly as performed in the Lightroom 3 beta 2 develop module. However, at this time Camera Raw 5.7 is unable to support further adjustments to the following settings or tools:
Highlight Priority and Color Priority post-crop vignette
Enhanced Luminance and Color Noise Reduction
Grain effects
Process Version

So the speed issues pertain to the re-rendering of your already processed images. In other words, LR2 is reprocessing your raw images using Adobe’s new algorithms. If the individual rendering of your images drives you crazy, there is an easy fix!
Right before you go to bed tonight do the following:
1) Open LR2
2) Select all of your images in your library
3) From the Library pulldown (not module) select Previews
4) In previews select render 1:1 previews
Now go to sleep!
When you wake up in the morning the annoying delay when you navigated between images will be gone.