Since Joomla 1.6 is available as the stable version, more and more customers choose Joomla 1.6 version to built their webites.
On the other hand customers, who have their websites working with the previous Joomla 1.5 version, tend to migrate their CMS to the latest version for various reasons :)
Before you get started migrating from Joomla 1.5 to Joomla 1.6 first read the following instructions to get more familiar with the migrating process.

Migrating from Joomla 1.5 to Joomla 1.6 Tutorial

Note that Joomla migrating is sometimes not enough since many of the extensions you use on your website may be not available for Joomla 1.6
First check if the extensions you need are available to download and work with Joomla 1.6
For example, here you can check all our extension we always implement on demo websites of our templates.