After reading about µtorrent, I downloaded a copy to compare with Transmission (which I've been using for about a year) since some other comments here implied that it was far faster than Transmission. I was more impressed with the µtorrent interface than I expected to be (for a beta), but I was really only interested in speed comparisons, since I'm happy with Transmission's UI already.

I just conducted as real-world a comparison as I could -- used µtorrent to download a 700MB, well-seeded file (the tracker reported 7000+ seeders AND leechers, regardess of the connections my clients made).

µtorrent downloaded the file in 1:09 (an hour and ten minutes), and I immediately fired up Transmission to duplicate the test. Same basic network activity and computer usage during both tests.

Transmission downloaded the exact same torrent in 0:39 -- a bit over half the time of µtorrent. YMMV, of course. But I will continue my ride on the SS Transmission, thank you very much.