If you use uTorrent then before you upgrade to the new version 2.0 you might want to check with your torrent sites to see if its allowed. Quite a few private torrent sites are banning the new version. If your on the old version you are still good. Out of the two main private torrent sites I use one has banned it stating the "unfairness" of it.
I use uTorrent but I'm on version 1.8.4 the one previous to the 2.0 The main torrents site that I use has a huge banner that says do not upgrade as it is a banned torrent and you will not be allowed to use it. So what is the big deal with uTorrent 2.0 and why is it banned? The new version has what they call UTP where it basically throttles itself. It also has been noted that it "favors" its own kind vs other bit-torrent clients. When it connects to other clients it gives preference and that is deeming it as un-fair by torrent sites. So basically before you click that upgrade button do some checking first so that way your not left trying to downgrade. You can also read more about it here: CLICKY