This tip is especially useful if you're on a 56k.
I dunno what the results are on DSL or Cable but maybe someone else would.
To increase your download speed on 56k check, Disable Peer to Peer transfer.
Now I know this says it will DRASTICALLY reduce your download rate. If you're on a 56k this is an UTTER LIE.
You're download rate will guaranteed be higher if you check this.
The reason being, bitorrent type programs are not made for 56k. It has to download a list of people useing the torrent and find the right people to download from ect. This is causing the program to download alot of information. (Alot in 56k terms, like I said I dunno how Cable and DSL would react.)
Disabling peer to peer prevents this process and instead you download directly from Blizzard.
Now my results have gone from 2-4kbps with a major difference in Patch downloaded, and actual MB downloaded (which could be a huge difference between the two, 5mb of patch downloaded and 10mb downloaded overall wtf?)
To a 4-6kbps and the downloaded amounts are concurrent.