Just do a search for "torrent" on versiontracker and browse through the bit-torrent clients for OS X. There are more than a few from which to choose. Transmission seems to be the favorite at this point.
I believe that the MTR v3 beta is Intel native. Version 2.66 should still work just fine for you on your MBP, though.
EDIT: You'll probably need to configure OS X's built-in firewall to allow which ever port(s) your particular torrent client uses. I had to open up port 9090 for Transmission...