I bought ACDSee Pro 4 on Saturday... they sent a message offering a free upgrade to Pro 5, which is nice. I agree with others Pro 3 was unstable, 4 was better, I hope 5 is really stable. Back in the OOOOLD days, ACDSee the viewer was by far the fastest way to view and organize my photos. I may drop down to the non Pro version if it's more streamlined. I really mostly only need to organize and rotate things with ACDSee, if I'm editing, I'll use Photoshop.