rTorrent when I'm on linux).
I love the streaming feature. I usually download movies and TV shows (no need to get angry, no Netflix or Hulu access around here!) and it's really awesome that I'm gonna get to play the media without having to download the entire file. Another really badass feature is the Drag-and-Drop file sending; you just drag and drop a file in the box, you get a link, you give the link to some people and they can download the file. You basically become a seeder for that file. Really amazing! Anyway, there's a whole blog post about the new version here, so, go check it out.
If you have uTorrent version 2.x, you won't be able to update it by clicking "check for updates" because it will tell you that there's no new version. So, in order to get the latest version, you need to download it manually.
I'm sure you'll love this one, leave some comments to let me know what you think.