I'm using Shadow's client. As far as I've seen the trick (for me, at least) is to only download one thing at once. For me, if I have two clients open, I get much less than half the dl speed. Also, with one client open, browsing the internet is no different. With two, it's unusable.

So, with one client open and my router's ports configured properly, I regularly get very high speeds. On average, I'd say I download at around 40KB/s. Yes, KB. I regularly see 60KB/s, and the last torrent I had open was going at 85-90KB/s for a whole evening.

Are you getting the same kinds of speeds?