I thought FSX with DX9 worked just fine for me, but I bought and installed DX10Fixer and WOW Iit's like FSX Next! MUch better looking graphics and way smoother. I haven't used any slider adjustments in the UI either --  just the default settings. Money well spent!

I did follow the setup instructions by Paul Johnson for Nvidia Inspector, the FSX internal settings and the FSX config.

Bruce