I actually found two different versions of the OSC external for Mac OSX. One is from http://barely.a.live.fm/pd/ and contains three Darwin files (sendOCS.pd_darwin, routeOSC.pd_darwin, and dumpOSC.pd_darwin) without any documentation or help patches. The other is from http://homepage.mac.com/atl/sw which only contains one Darwin file (OSC.pd_darwin), but does not contain documentation or example patches either. I'm not sure what the differences are between the two builds of OSC, or how to use OSC in PD.
check the /doc directory in the farmersmanual version. it has an example patch that shows you how to use OSC. it's really quite simple: set up a send object with a port number to send packets to, and a receive object with the IP address of the the send object's machine
By the way, what makes OSC any better/worse/different than netsend/netreceive, or netclient/netserver?
OSC works in Pd, Max, SuperCollider and other software (even Flash and Director). That seems to be reason enough for most to choose OSC over netsend/receive.
cgc