Nope, not papers as in publications, but Papers as in the product of two enthousiastic biochemists (page not updated recently). Just today, this morning, Papers version 1.1 was released, meaning it is in active development.
Papers is a sort of library manager, like Bibdesk. However, its purpose deviates from that of Bibdesk, and (hopefully, after tighter integration development), can be used side-by-side. Perhaps Papers can be better described as a scientific article reading workflow integrator thingie. It allows you to easily match articles with information (meta-data), and it organises the PDF library according to your preferences in a comprehensive directory and file structure.
Then it allows you to go fullscreen. Fullscreen should really have been written with a capital F, because if you want, you only see the contents of the PDF file on your screen, no clutter or anything else. Info- and note-windows and control bars can be made to appear if wished, but perhaps the uncluttered version is what we need to enjoy reading our articles on a screen.
It has a good integration with PubMed, which is not really of interest to non-bio or -med folk. It does have an internal browser plugin (which uses Safari), with which you can search for what you want, and upon encountering a PDF file, (allows you to) downloads it automatically, and adds it with its metadata to the library.
It has some more functionality, but if you’re interested, head over to their website.
There are still some usability issues here and there, but all in all, this package shows much promise! I have requested a few more features here and there, and it’d be interesting to see if they will appear. So far, response from the authors has been swift, personal and informative.
Oh, by the by, students get a 40% discount on the total price of 29 euros.