I also searched for good and stable version of utorrent cause of my own interest and reached to this decision -
(+) should use the 2.2.1
(+) any latest stable version of utorrent
2.2.1 - I use 2.2.1 build 25302. I use the latest build of 2.2.1 which is stable and also approved by all the trackers. its light, it uses very low resources, small but fast and does every (torrent) download job perfectly.
Any latest stable version - they are bug free, stable, approved by the trackers but they uses more resources than 2.2.1, they are full of features (most of them are totally unnecessary). So u have a good pc, good RAM good CPU, dont even worry about its resource problem...
There is another issue. every utorrent till v3.1.2 has a common bug. They cant (force) re-check the files if we use the magnet link. Up until the Piratebay magnet link incident, nobody noticed it cause people didn't use magnet link till then.
Lastly my opinion, 2.2.1 is better than others. I used latest till now but i downgraded it and using 2.2.1. I dont care about the the magnet link bug cause i dont download much from piratebay. So i suggest you should use 2.2.1