My desktop is a dual boot with win7 and LMDE on it. It used to have win7 and Linux Mint 11.
In both instances, I can pull about 10-11 times the download speed when running windows as I can when running linux.
Both are installed on the same 120GB SSD, use the same network card, video, etc.. There is 16GB of memory installed, and both installs are 64bit.