Surely we have to have an exception for IE?
Yeah, IE sucked since its inception, although with IE8 they've finally come around to having a useful product, at last. I still hate it, but at least I can use it without screaming at it constantly, when I have to (MSDN downloads, Windows Updates, etc.).
The products that Microsoft developed from scratch are generally better sooner, than the ones they bought from somewhere else (like IE, which was Mosaic, the poor precursor to Netscape). The Microsoft technique, of making whatever they sell into the de facto standard by stomping everybody else, bites them in their own ass fairly often, and IE is the classic example. They were stuck supporting its broken crap for many years, until they finally gave up and started doing what works, with IE8.
Just as Vista was the best marketing campaign ever done on behalf of the Mac, IE6 was the best marketing campaign ever done for Firefox. Microsoft is still the market leader in both those categories, but they took some serious hits by producing crap.