I can't bring myself to rely on Javascript to get IE to work for something as essential as the actual tags and structure of the entire site, nevertheless one that would be browsed by near 50%+ of the population!  

HTML5 is cool, but WC3 was right.  It's simply just not ready yet.  Besides, I'm having more than enough fun just playing with CSS3 that easily degrades.  I've waited this long for semantic structure, a little longer won't kill me.