What's the difference in versions of Joomla Content management systems i.e. Joomla 1.5, Joomla 1.6 and joomla 1.7 ?
Primary Variations between 1.5 and 1.6
Refined Access Control Layer One-click upgrades of core Content management systems
J1.6 to at least one.7 is greatly an incremental upgrade - plenty of small unique features to user workflow.
J1.8 is going to be known as J2.5 - try not to request why.
1.5 and 1.7 are long-term support for several years joomla 1.6 is really a intermediate version and d'ont have support yet!