I've been using the Sonarworks software since version 3 and I'm satisfied with it. It won't make your room sound better (use acoustic treatment for that), but it will make your speakers perform better in any room.
As for the headphones version, I use it with all my headphones for mixing and sound design. I was mind blow by how much it improves the sound, with the default average profile, of a very cheap pair of headphones like the Behringer HPS3000. I mean... the HPS3000 sound really bad out of the box, but can actually sound acceptable with the Sonarworks calibration.
Like with everything software... try the demo before buying, just to make sure it works well on your system and it plays nicely with your cans.