I just completed a new theme for WordPress and I decided to get it to validate. I usually don’t bother, but this time I decided to make sure that it would validate. I used to think validation was of dubious value. It’s easier just to make things work in Lynx. If it works in Lynx, then it’s ok for the search engines.
Now there are things more important than search engines and one of them is maximum usability. XHTML means that your site is usable on even more formats. This could be very important in the future. Another great thing is the sense of accomplishment. There is nothing like the accomplishment of having your theme validate.