I'm using in a extensive way tags in mi site:

www.madridout.es/i/tag/economia

And after last version (2.6.5), I had problems with cache in articles listed by tags mode as descripted in that post:

getk2.org/community/New-to-K2-Ask-here-first/169543-Bug-in-Version-265-Tag--Cache

However, thanks to Stefano Gargiulo we found a solution and now I have make some improvements in order to have meta description and meta tags for each tag page. This is because Google Webmaster tools used to found many duplicate descriptions in tag pages (/itemlist/tag and new ones with advanced sef settings developed by joomlaworks team)

So... my solution for tag pages is to add just after defined('_JEXEC') or die;

This code: