Our own site on invisionpower.com is now running version 4.1.16 with all the new features. Have a look around and see what you think! My personal favorite is being able to press cmd/ctrl+enter to submit a reply. It is a small change but sometimes small changes make all the difference.
We have also released a beta for any clients who are interested in using the latest release before it is officially available. The alpha and beta forum has more information (clients only) if you want to learn more about using beta releases.