Ours used a roller for the intake, and a scoop. It's a little slow, and we also have trouble with jamming when picking up two side by side frisbees. We tried the trick of angling the intake roller so when encountering two disks one gets sucked in first. This ended up making the single disk pickup less reliable.
We are currently designing and rebuilding a new arm as a summer project.
Could I request that people link to video of their working arms?
Prototype testing:
http://www.youtube.com/watch?v=XVD6P3wNRUg
Integration testing:
http://www.youtube.com/watch?v=rNaJeDeVASo
Final testing:
http://www.youtube.com/watch?v=7XSihXrLHZY
Match footage:
http://www.youtube.com/watch?v=BZ0g1o40oPA#t=01m22s
I should note that we designed the arm to be easily replaceable if damaged, which was necessary in Richmond. This was cited as one of the reasons we won the Quality Award at that event.