There's a big gotcha waiting for anyone who has processed lots of RAW photos through Lightroom 1 or 2 or through Adobe Camera Raw prior to version 6. Adobe introduced process version in CS5, ACR 6, and the Lightroom 3 public beta.

What does this bit of jargon mean? Well, it means that Adobe has introduced a whole new way of reading RAW data.

The implications can be rather significant, if you've done any sharpening, noise reduction, or vignetting with Lightroom or ACR. You'll likely find that the results of these operations are more pronounced when you use the 2010 process. How significant is the difference? It depends. Sharpening for example, will probably show little difference if you only applied capture sharpening -- and true to its meaning, you were very gentle. If you were aggressive with the settings, you'll likely be unpleasantly surprised.

This means any presets you made for sharpening, noise reduction, or presets will likely need to be updated.

Lightroom 3 public beta and ACR 6 will check the RAW file metadata to see if you previously applied any changes with the older process. If so, they will open the files with the 2003 process. That will keep thousands of LR and ACR users from writing to Adobe ans asking, "What happened to my photos!?"

You can choose to open previously worked files with the 2010 process from the Camera Calibration panel. Likewise, you can choose to open up unworked RAW files with the 2003 process.

The 2010 process is a definite improvement. But, isn't change wonderful?!

Matt Kloskowski has something to say about this:

http://lightroomkillertips.com/2010/lightroom-3-beta-cs5-and-sharpening