Not from mine. Give me solid testing every day of the week over meeting a spec produced by a committee. Validating can be part of testing, but too many people think that it is the same as testing.
If you put <b> into an html 4 or xhtml document, it will not validate. But it will work on every browser that anyone uses and it will work on any browser for the foreseeable future.
On the other hand, I used a popular theme with a CMS that is xhtml compliant and all the pages validated perfectly. It looked great on firefox, mozilla and opera. In IE it produced a page, that was incredibly difficult to read.
Give me thoroughly tested over validated any day.