I recently switched from Windows to Mac and I had been using uTorrent for my downloads. After switching I couldn't find any decent places where Mac Torrenting clients were discussed, but I have tried a few of them.
Bog standard BitTorrent: Fairly usable, does the job well with pretty decent features.
Tomato Torrent: Terrible interface, clunky to set up YUCK
XTorrent: You have to pay for it otherwise it is nagware and cut down so you can't go past a certain speed for downloads/uploads. On the flipside, nicely made program.
At the moment I am using the normal Bittorrent client, but if people are recommending Transmission, I'll give that one a go too. I was going to browse the boards today and check for a similar thread; how handy that there is one straight at the top of the page. Cheers for the suggestions