Seoace a South African SEO service  has officially switched to Joomla to manage the content on our website, we have researched many different cms systems and consider Joomla to be the most advanced SEO compatible cms available on the market.  Using Joomla in conjunction with the sef404 component has yielded fantastic results for us, there are a few quirks but these seem like the may be resolved with the realease of Joomla 1.1 which we are very excited about.