I know alot of BT fans around here say that the Shareaza BT client is crap.
I've run Shadow and Shareaza on the same file at the same time and Shareaza is ALWAYS faster for me.
From what I have seen in the first clients all the way to the newest Shadow and 3.3 they all basically do the same thing with newer features. The only one that stands out is Shareaza, which is now trackerless as well.
One problem I always had with Shareaza was if the client was a leech. On the early client it never uploaded, and on the later clients which did, they seemed to close when finished which is against the idea of BT. Well it seems the people at Shareaza are here to please and are making jumps and bounds with their software, which is improving dramatically with each new version.
Upon completion a copy of the file is moved to your download directory while the other is left in the Incomplete folder to continue uploading. Not only does the file continue to upload after completion, it also leaves a "sd" file for reseeding the file later, though I have yet to try it. If you don't believe it then here is a screenshot for you...
I suggest you get Shareaza and try it out, especially if you low speeds with the other BT clients.
If you don't know already it also connects to G1, G2 and eDonkey all in a very nice GUI...