I have donwloaded and experimented with both beta 3 and 4. I love it. Great controls. My major disappointment is that it won't handle my very large images. I do panoramics and mosaics. I frequently have images as large as 8,000 x 20,000 pixels. As best I can tell, LR doesn't display (or even import) images over 3,000 x 8,000 pixels. I hope they fix this in the final production version, otherwise I am outa luck.