PHP version 5.3 has been released, and although it looks great, all my code already works fine. I don’t see what this new version offers to justify upgrading and working through possible issues after the upgrade.
Should I upgrade anyway just for good practice, or is an upgrade not needed unless I am actually using the new features?
You might consider upgrading just for the "Improved PHP runtime speed and memory usage" and bug fixes. Source. I would also say that if you are using create_function anywhere, you should upgrade and replace that ugly, nasty mess, with the much cleaner lambda. Here is the migration guide from 5.2.