I tried the Beta test of Lightroom, and it didn't seem to do anything for me. I watched a Demo at the Photo Expo last year & asked myself "Is That All There Is?" I find that the free program Picasa does a very fine job of allowing me to organize my photos. And now that CS2 7 CS3 come with Bridge, and that takes care of RAW conversion, batch processing, etc., I'm not really sure of the need for Lightroom.
I am using the Beta CS3. When I switched from windows to Mac I only had WIndows CS2, so I downloaded the Beta for my Mac. The Beta version has one big flaw - the Brushes do not show - all that shows on a brush are the crosshairs. Adobe indicated that it will be fixed in the commercial release due out this spring.
Since I only have used CS2 on a slow Windows machine & CS3 on the speedy Mac, I really cannot do a comparison. But I can say that I am happy with CS3, and I plan to upgrade my CS2 to CS3 when it is released.