I use utorrent instead of Azureus because it is light weight and quick, the one drawback that I have noticed since I have been using it, which has been about 6 months, is that it slows my internet connection down a lot, almost to an unusable state.
For a while I had my upload limited to 10Kb/s with utilized 22% of my upload limit from my ISP of 45Kb/s. We have Comcast and we upgraded to their "blast" service which gave us a DL rate of 16MB/s and we have tested our upload to be around 350Kb/s so there should be no problem with having the UL rate at at least 45 or 50.
Why is my internet so slow when I use utorrent?