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.
>The qBittorrent project aims to provide an open-source software alternative to µTorrent.
though in my experience it is more of a memory hog and buggier than utorrent. but that doesn't stop me from using it