On opposite ends of the scale are Transmission and Vuze.Transmission is small, fast torrent client that does one thing well. Vuze is geared toward people who use torrents primarily for video entertainment. It handles any file format as well as other bittorrent clients. However, Vuze includes a viewer for downloaded video files.
Out of that bunch, Transmission is the most often used, in my experience.
And, I think you should find it simple to use....
Just curious - What kind of files do you need to use torrent software, rather than the usual download methods?
In my opinion, torrents don't appear to be the best way to go anymore, particularly on a Mac, where the newer OS X systems try to "protect" you from using software that it thinks is from "untrusted" sources.
And, this forum doesn't provide help with getting (or using) illegally downloaded software, which remains a common use for torrents.