For those who just started usingit is being phased out Feb 24, 2012. is already here and available for download at .org and here is a message from their site regarding the update:
Along withsuch as advanced search and automatic notification of core and extension updates, the Joomla CMS for the first time includes multi-database support with the addition of Microsoft SQL Server. Previous versions of Joomla were compatible exclusively with MySQL databases.
It will be fun trying to search for all the newfeatures. I will let you know what I find. From initial glance at the new version it looks like a big overhaul and lots of great features. If you are using , there is an update package available to upgrade to Joomla 2.5.