Picasa, the popular free photo management software made by Google, has finally made its way to the Mac. The application has long been noticeably absent on the Macintosh - especially given the fact that it has been available for Linux (which typically lags behind Macs and Windows) since 2006. It’s also a direct competitor to Apple’s long running iPhoto product, which has come with all new Macs for years. So how does it stack up?In my brief testing the application seems to be very snappy (much faster than iPhoto), though it lacks the sleek look of Apple’s products. Photos import quickly, effects are easy to find and apply, and most things are intuitive, though the folder browsing can be a little confusing. It might not be as pretty as iPhoto, but I won’t be surprised if power-users make the switch (or at least consider it). One of the biggest differences between Picasa and iPhoto is that Picasa doesn’t move or reorganize images, but instead keeps track of where your images are scattered across your hard drive and allows you to view them in one place. For users that manually manage their photos by sorting them into folders, this is a very welcome change. In contrast, iPhoto has long transfered your photos to its own library, and encouraged users to sort their photos through the app itself.Given that iPhoto has come preinstalled on every Mac for years, Google is doing doing everything it can to make Picasa play nice with your existing library. While users can typically modify any image on their hard drive directly from Picasa, all images in iPhoto’s library are treated differently: the application will copy these images to a new location, and only then apply edits. The application also allows users to revert back to previous versions.Picasa is a welcome alternative to iPhoto, but it’s still premature to drop iPhoto entirely. It’s highly likely that Apple will unveil a new version of iPhoto at tomorrow’s Macworld keynote, and you can be...