After installing Snow Leopard a few days ago I took the time to open Activity Monitor to see what programs were running in 64-bit and which ones were left in 32-bit. To my surprise I saw that my copy of Lightroom 2 was running in 32-bit still.
Now I was really disappointed to see this because I though Lightroom 2 was supposed to run in 64-bit. So I went into my applications folder, found the Lightroom 2 app, and pressed Command i to get more info on the program. There I found the culprit. There was a box that was checked for the app to run in 32-bit mode.
To fix this problem simply uncheck the box and open the app. When the application loads you should see that it now says 64-bit on the tittle screen. Running Lightroom in 64-bit now has given me a huge speed boost all over the application from load up time, to editing, and export.