The minute I saw this I knew I wanted it! The price is a bit steep, but to me, the benefits are well worth it. The interface is slick and clean, very much like iPhoto or Mail. I love the fact that I can open a PDF in Preview or whatever, Mail it (and I can set what mail application to use in preferences, which, being an Entourage user, I love!), open it to full screen, etc. Being able to specify authors, and to add identifying tags, is going to be a big help in organizing my hundreds of PDFs. Did I say hundreds? Yep helped me discover that I have 2283 of them scattered all over the place. I was stunned by how fast it found them all. I love the automatic tagging that Yep does; very helpful. Showing all the info about a selected document is wonderful, saves steps, and the "loupe" is great for quickly zeroing in on a document to get a specific snippet of information.

I have the feeling this is one application I will be using for years to come.