UTorrent for Windows has been around since September of 2005. BitTorrent Inc. acquired uTorrent in 2006, and roughly two years ago work on a Mac version began. An alpha version of the Mac client leaked on to the public earlier this year, but this version has significant improvements.
A BitTorrent Inc. rep told TorrentFreak that the company is now working to fix bugs with the PowerPC as well getting uTorrent to run on the Tiger OS.
The new Mac uTorrent can be downloaded here.