Should I Upgrade to Joomla 3.0?
Joomla! has changed how they do their versioning. STS and LTS are no longer relevant.
Should you upgrade to Joomla! 3.3.x or higher? YES!
There has been a lot of questions surrounding the recent release of Joomla 3.x regarding which version should be used to create a new website.
It is recommended by the Joomla team, and Joomla professionals around the globe, that you do not use Joomla 3.0 for a production site for a multitude of reasons, the main one being that it's not a Long Term Support release and is still in active development.
Currently, Joomla 2.5.x is a LTS (Long Term Support) release that is proven stable and has access to thousands of compatible extensions. The LTS releases are supported for 21 months, giving you/your clients a solution that can and should be used for longer stretches.
While Joomla 3.x has some serious improvements under the hood, including a responsive template for the Front and Administrator side of things, it is a STS (Short Term Support) release that is recommended for developers and early adopters.
If you constantly find yourself wanting the latest and greatest in technology for your website and don't mind tinkering around with things to get it working, then Joomla 3.0 is probably a good choice for you. Make sure the extensions you want to use on your website have versions ready to go with this new version (Versions running on 2.5 are not necessarily going to work on 3.0).
Should you decide that this is the way you want to go, then don't forget to upgrade to 3.0.x, 3.1 and 3.5 when they are released. These new versions will contain bug and security fixes that may or may not be driving you mad.