Great tool for squeezing just a bit more perceived loudness from your track.
For sound design and individual sounds you can go crazy, just experiment with "effect" and "curve" sliders for interesting results.
On the other hand for mastering usually less is really more.
One thing that I personally miss on this plugin is a bit more complexity, more options to tweak and generally take more control of the given effect.
Definitely a great tool, using it on almost every master, usually in 20-30% range. Feel free to experiment and be creative!