You say you want a revolution
Firefox initially displayed my blog a little wider than the screen, but it took only a minute to adjust my blog's template accordingly. And Firefox actually lacks an annoying glitch that IE has. The "BlogThis!" at the top of my blog is the proper (small) size in Firefox, but in IE it somehow defaults to a larger size. This makes the top Google bar larger than it should be, but after going through my HTML a dozen times, I still could find no good reason why the font size was so large. It's fine under Firefox...
Many websites will look slightly different under Firefox, and some will look very different, because Microsoft has never programmed Internet Explorer to official HTML standards, and Firefox was designed from the ground up to adhere strictly to standards. It should be interesting in the coming months as Firefox gains greater market share, which will force Microsoft to improve IE security (if that's possible) and IE's adherence to official HTML.
Microsoft should be concerned. I, who until earlier this year always used Windows, who until today always used Internet Explorer, am starting to convert.