I don't have any delusions that I'm the first to discover this little gem, but since I only recently saw and took a recommendation to check it out, I wanted to give it a little airtime.
It displays your energy, combopoints, and energy ticks into a compact little interface that you can put anywhere on your screen. I've nested mine just above my attacks.
The obvious and expected benefit is that during combat you can see exactly when your energy will tick so you can unload that mangle or shred at the optimal moment. One thing I didn't expect is that you can see your ticks even when you're at 100/100 energy...so when sneaking up on an unsuspecting victim you can land your opening move just before your energy ticks by 20, which effectively reduces the energy cost of your opening move by 20.
I now get why sometimes it seems easier than other times to land the Pounce/FF/Mangle/Shred/Shred combo opener. If you have plenty of time, you got lucky and pounced just before a tick, but if the timing is tight you got unlucky and Pounced just after a tick.
So for this feral druid, RogueFocus gets two snaps in a z formation.