This handy little feature is only available for users who have opted into the Beta program. This can be done in the client settings menu.
There are some other updates in the beta which are also pretty nice. These include reduced CPU usage when drawing animated images or videos, fixes for video playback performance on Mac OS X and Linux, improved capture performance in D3D9 games and improved audio/video synchronization to name a few.
For those who are part of the beta then go ahead and start getting your FPS. For those that aren't go ahead and sign up. There really is no reason not to.
What do you think of this? Is it a welcome change or a pointless update?