I use wp-syntax for syntax highlighting on Wordpress, but I changed the code to use:
<pre class="sh_html"> </pre>
instead of:
<pre lang="html"> </pre>
I did this for future xhtml compliance. I also did it for shjs, which uses class too. Ultimately I think that syntax highlighting should be a client side process, especially for code snibbets which are embedded in other markup. Complete files are much easier to send through a web server filter (like source-highlighter) for faster processing and cacheable content. Wordpress does some wacky internal formatting and filtering like changing quotes and such, and thankfully wp-syntax avoids all that, so I'm sticking with it for as long as I use Wordpress for rendering output.
I would also like to use <code> tags along with <pre>, but that makes some of my transformations with XSL a little more difficult to use them together. I may end up switching to only using <code> - in that case I'll have a lot of tags to change over!