Well, Flash vs. Silverlight goes much, much deeper than games (the number 1 use of both is streaming video), but this is definitely interesting
Unity needs some competition in 3D browser-based gaming. Microsoft Word was basically the exact same program for from the Windows 95 version, right up to Word 2004, with the same features. Maybe 1 small feature a version was added, because it reined supreme and there was really no competition. But now, Open Office has made Microsoft step their game up. I am actually having to relearn Word, Excel and Access all over again from the ground-up because they have added so many new features. In just 1 or 2 versions it has been more updated than it has in its entire life, all because it finally has some real competition that is eating away at its userbase. I will be interested to see how this affects Unity for browser-based games!