Windows update is the only site that does not support it, and you all know why =P. I love the advertising and pop-up blocking (If havn't already look for a plugin called 'AdBlock', If you wan't my block list let me know). If you still have to use IE but can't live with out the tabs there is Maxthon (Was MyIE2) which adds a tabbed interface to IE and a LOT more funcitionally. Now to answer your question, Yes I do use firefox, and can't live with out it.
Gear:
3 x GoPro Cameras
1 x Canon S100
1 x Nikon D5100
1 x Sony DSC-TX10
Apple MacBook Pro 15" (Retina Display)