The majority of our clients are on the Joomla platform. Over the past year Joomla has been churning away at upgrades. Leaving the Joomla community wondering how hard it will be to update their joomla platforms.
It appears Joomla has plans for a major upgrade every 6 months. Upgrading from Joomla 1.5 to the newer versions requires template changes and other changes. Not all of the extensions have been upgraded yet either. So Joomla 1.5 is still the best choice to deploy new websites if you want all of the bells and whistles to work. But one day, it will be time to upgrade from Joomla 1.5 to one of the newer versions. It is best to allow the new versions some time on the market before upgrading to make sure it is stable and that the extensions and template you want to use will work.
The good news is... if you wait long enough... Joomla is saying when 1.8 comes out, there will be a 1 click upgrade from previous Joomla versions (1.5, 1.6, 1.7). Who knows how well this feature will work, but it's worth waiting to find out!