"Photoshop" your flight simulator. That's what this is and it's real good at it. While it's not a real must have, it's great to fine tune the end result on your screen.
Never noticed a performance hit. No matter if it was on low or high end hardware. The frame rate stays the same.
All the pre-sets are nice demos giving you an idea of what can be done. But I doubt that you'd like to live with them. The custom mode however gives you very fine tuned control over everything the plugin does. A few changes here and there and the result can go from great to almost photo realistic.
I think it's priced a bit too high, but I can highly recommend this tool to anyone.