I´am using Bitcomet and love it but Azureus and uTorrent are two great bittorrent clients as well and I know that a lot of people are using them. The AureusWiki site has an entry that tries to help you to download your torrents faster. They post some interesting links in that article that deal with common problems and settings that slow down downloads. They provide a chart for example that take different upload speeds and define other settings that are optimal for good download speeds.
