BitComet recently cut a bit of software from itself that gave it speed, so its really no faster then normal Bittorrent. The fastest are uTorrent and Azureus. I personally use Azureus, just remember to remove your old versions of Java otherwise Azureus gets memory leaks Other then that Azureus is fast, multiple torrents and gives you more information then you'd know what to do that, plus it's Opensource Software.(the old versions are like 'Java 1.5 update 4', just remove these until only the newest update exists)
I use BitComet since 2009. In fact of what other people think, BitComet is much faster that Utorrent. I didn't tested it agains Azureus. I recommend it to anyone. It's clean, very fast, you have priority option if you download more files, you can also download a movie, starting from beginning, so you can start watching while still downloading. The only problem is that it's not quite good for upload... but if you want a program to do a job well, Bitcomet is what you need. Cheers to all!