I've been using Papers now for nearly a year and it is one of my top favourite and most useful apps I've ever bought.
I'm a geology Ph.D student and tried to use Sente but found it too biomedical-centric to be practical for me.
A few of the gems that I find especially useful:

- the ability to find & download articles directly within Papers

- the 'Authors' tab which searches the latest publications by a chosen author in your library - fantastic way to be up-to-date on a leading researcher's findings

- the export reference is easy to paste directly into the manuscript you're working on before you do the reformatting for the journal in question

Requests and suggestions for improvements:

- add some sort of highlighting functionality as in Preview app or Skim. While the Notes tab in Papers is useful, one tends to forget to look there if it's not selected. I find myself opening pdf's in Skim and making highlights there, then saving and returning to Papers.

- I love auto matching function to get metadata, but it only works for newer publications in my experience
(Google scholar integration is awesome I must say!)

Highly recommended app if you read a lot of articles, and it has inspired me to scan my paper reprints and go paperless :)

Fantastic piece of software, well done!
Now I can distribute my presentation to colleagues who weren't present for my talk and they can still have the same audio-visual experience. Really useful!

Great to see some geology apps since most are windoze. Keep up the good work!

Fantastic app! After trying it for one day I bought it. It's exactly what I was looking for in that I can finally control EyeTv, Mplayer and basically any other appliation using my Apple Remote and a bit of cut and paste Applescript if I want to add functionaluty for more apps. Great interface, great functionality, great price! Recommend anyone who likes using FrontRow with their remote to give this a try!

Love it more than Front Row! This would be perfect if I could just watch my avi and other movies on my intel mac. Can't wait to see how this develops.

10.4.8 caused my Intel mac to have a kernel panic and got stuck in an infinite restart loop. Other people in Apple discussions have had the same problem: http://discussions.apple.com/thread.jspa?threadID=668161&tstart=0