As for the IE conditional comments - their use in browser sensing is actually a misuse of the code since the tags were originally introduced so as to allow an HTML like markup to be used for converting files between different Microsoft programs.
<![if MSO 9]>code specific to Microsoft Office 9 goes here<![endif]>
We already know that the conditional comments don't have a problem with two digit version numbers since Microsoft Office is already well into double figures and version 10 didn't break the conditional comments.
All we need now is to convince everyone who is checking a single digit from the user agent string, to use better techniques.
Until that issue is sorted out, microsoft may have to call IE 10 version 9.10 and IE11 version 9.11
I have yet to see any browser detection script involving the useragent that works correctly. I have Firefox 3.0.5 identifying itself as IE 99.1 in the useragent and none of the pages doing a browser detect manage to work out that it is Firefox rather than IE. They all believe what the browser says it is even though the version it claims to be doesn't exist rather than testing for what the browser really is.
Pages using conditional comments do correctly identify that the browser is not IE despite what the useragent says. Also we already know that conditional comments don't have an issue with double digit version numbers.