Please note all the details here have only been tested to work to improve download speeds of freely distributable copyleft materials such as Ubuntu full DVD images.
If you're like me, you've already covered the basics (I had "green smiles" and "open nat") but if not, you may want to start with that.
My problem was that I was only connecting to 20-30 peers out of thounds of seeders and my down speed for a single torrent capped out around 150-170 kB/s. I discovered that the max number of connections was set to 40, I don't remember changing it - hitting reset seemed to indicate that by default Vuze limits the max number of connections to 50:
This number maps directly to the number of peers in your swarm. And mine was set much lower than the recommend "Good Settings" - I went ahead and just disabled it for now:
And I was pretty happy with the results: