BitTorrent is amazing. It just works. Anyone anywhere can create a torrent of their files, dump the magnet link somewhere, and everyone else can reliably retrieve it. It is self-reinforcing; the more people using a torrent, the better the robustness, redundancy and download speeds. You can often get better speeds from downloading something via torrent than from a web server. It's an open protocol that is relatively easy to implement, it has a diversity of lightweight clients for all OSes and is fairly resistant to censorship. To me it's pretty much perfect tech that solves a real problem. I hope Bram Cohen got rich off of it somehow.
Wish browsers had built in support for it. Imagine if by default most downloads were through BitTorrent, and your browser would then seed the file for 1.5x the download size and time.