The now-stable, native Mac version of the beloved Windows client sports a Mac-like UI, designed for downloading many torrents at once, while also being pretty light on system resources. It doesn't look like there are a huge amount of changes between the last few builds and this one, though a few pretty annoying bugs have been fixed, and anyone holding out for a stable version of the client should now be pretty pleased with how it handles. We haven't done any formal tests yet to compare it to now-Mac-favourite Transmission, but if you're a heavy torrenter and try out the new build, let us know how it works for you in the comments.
uTorrent is a free download for Mac only. Note that while the site still says it's beta, uTorrent has announced it as the stable build on their blog (and the build numbers match). It seems like they just haven't updated the images on their website.