There are a lot of questions about the differences between FSX and P3D as far as how it runs, how it is set up, hardware, etc.
Might be a good idea to list what you have found to be different in using P3D, both good experiences and bad.
Off the top of my head I can think of a few:
1) No start screen - handled beautifully by the freeware SimLauncher - available in the Flightsim Library
2) default LOD Radius is 6.5 as compared to 4.5 for fsx
3) Requires little or no tweaking right out of the box
What have you found?