I have installed Landclass Scenery for San Francisco and Los Angeles, and all stops in between...

...!
LOL...!
It certainly improves all the scenery, texture, hills, etc, and it makes the scenery accurate according to the relief maps of the areas.
It has little or no effect on my frame rates...

...!
Well worth installing if you fly over a limited area, (The Land Class Scenery covers certain defined areas and you have to select them individually).
Cheers...

...!
Paul.
(England).
P.S. ...the only thing to remember, if you fly on-line with your mates, they wont be able to share your lovely new scenery down below....Tee-Hee...

...!
Win 8.1 64-bit. DX11. Advent Tower. Intel i7-3770 3.9 GHz 8-core. 8 GB System RAM. AMD Radeon HD 7700 1GB RAM. DVD ROM. 2 Terra Byte SATA Hard Drive. Philips 17" LCD Monitor. Saitek Cyborg X Fly-5 Joystick. ...and a Briggs and Stratton Petrol Lawn Mower.