Comment on Azureus

uTorrent is the best torrent app for Windows. It's lite and fast. For Mac we have Azureus and Transmission. The first one is JAVA, so it's bloated and consumes lots of RAM. Downloads are a little faster than Transmission, but keep in mind torrents are more seeds-dependent .
Transmission has the best GUI of all, lacking the speed of uTorrent for PC.