I use Lightroom 4 since it has become available and I'm still excited about its processing capabilities. I've had one minor gripe though: browsing through pictures wasn't at all smooth and it took too long before even the small thumbnails showed up. Thinking that the hard disk's lack of speed was causing this, I moved the catalog with its previews to my other faster drive where the operating system resides. This improved the scrolling experience and so I bought and installed a solid-state disk (Samsung 830 128GB) and the catalog and previews were moved to the SSD. That really improved things quite a bit, scrolling doesn't show large delays anymore before I see the thumbnails, although it's not as perfectly smooth as scrolling in Google Picasa. Another big improvement came from creating previews for all pictures in the catalog. Go to "All Photographs" in the Catalog and then to menu Library -> Previews -> Render Standard-Sized Previews. This is something to start off when you're not using your PC for hours, it takes quite some time. After that you won't have to wait for previews to be created when you're browsing through the catalog or whatever subset. Just wanted to share this :smile:.