It's nowhere near as perfect as utorrent once was. But it's pretty good and I have plenty of extra memory (it's currently using 305mb while seeding 40+ torrents, dropping down to 65mb if I pause them all.)
I wouldn't be surprised if qbittorrent predates uTorrent; Wikipedia says it dates to 2006. But it wasn't popular on windows until uTorrent started doing dodgy things.