IE 10 preview was useful when you could install it on a running system. Having to install a whole VM *just* to play with the browser is such a hurdle that I think that many like me just won't bother. And, lo, IE is becoming increasingly irrelevant: there's already so many things that not even IE 9 does well that people are moving to other browsers and from where they are unlikely to move back. Lots of corporate are Windows 7 + IE 8 + A.N.Other browser. Stats from a large site I know of are: IE 9 is about 10 % worldwide but has hardly grown since the spring; IE 8 is still king of the heap at around 25 % worldwide but down around 10 % since the spring, most of whom seem to have gone to Chrome.
Initially MS indicated a release of IE 10 in the autumn of this year but since they decided to roll it into Windows 8 the fail whale has definitely arrived. The hardware acceleration in IE 10 is impressive only until you realise it is currently of very little relevance outside demo-space: sites are not going to go back to "works best in IE", because it would seriously fuck off influential tablet strokers, so hardware accelerated games (and ads) will have to wait for broad browser support. By the time IE 10 is released, no doubt with the stupid rider "works best with Windows 8" - why else would they be tying the development of the two together? - it will be available and good enough for Opera, Firefox and Chrome and maybe even Safari (I think it already is for the I-toys).
In the meantime, and independent of their version numbering schemes, Opera, Firefox and Chrome continue to trailblaze with interesting new extensions for HTML, CSS (paged media, yay!) and JS and are available in the real world for developers to work with. This is the only way to make sure that future standards are any use. Pity that MS still hasn't understood this.