Upgrading, which version?

Greetings!

I am looking to upgrade from version 1.5.6 to a more recent version, but I have noticed there has been quite a bit of development and several releases. Which is considered to be the most stable version? Which version should I consider upgrading too or should I even bother at the moment?

Thank you for your input. It is greatly appreciated.

Always the latest - 2.3.2 as of now.