I freaked out a little when I started seeing do-whatever-you-want creep back in when I first read diveintohtml5.org (mirrored: http://diveintohtml5.info/).

Sure, you save some (or a great deal many) characters, but at the cost of making everything that needs to work with it more complex. (Browsers are a large slice of this pie, but by no means is the only slice.)

I'm going to sit back and wait for the cycle to come back around to XHTML-like correctness again.