For the people who still think there are only "cosmetic changes" I'll give a rough rundown on what's new "under the hood" (feel free to correct me):
- single core, single thread -> multi core, multi thread
or in other words: my quadcore hyperthreading CPU will not freeze himself to death while performing FS calculations. The Intel generations in the last years from Nehalem to Ivy Bridge to Haswell did not increase the processor frequency by any means. Moore's Law is broken for several years now. I guess it's because of Heisenberg (the physicist, not the chem teacher!). FSX won't get any faster with only a single thread.
- All on CPU -> CPU + GPU
The graphics calculations are now where they belong: on the GPU. The GPU still has a lot more performance potential than CPUs simply by adding shader units or improving the DirectX depending microcode. The performance boost between GPU generations is still impressive. Also, direct calculations on the GPU don't use up precious VAS... so less OOMs even in 32bit.
- dx9 -> dx11 (incl. volumetric fog, new lighting, dynamic shadowing, tesselation, object instancing)
A little reminder: The step from FS9 to FSX was DX9 to DX9 + totally bugged "DX10 preview". I just spent a lot of money for ironing out the "DX10" bugs.... GNAAAAH!
- flight modeling can be made externally
Because of backward compatibility the limited flight model of FSX is here to stay. So they opened up the model for injection of external flight models. My understanding is that this was what A2A accomplished with FSX all by themselves. I maybe wrong, feel free to correct me.
- 64bit modeling tools in the free SDK
You better ask Bill about it... LM uses his quote as advertisment here:
http://www.prepar3d.com/news/2013/05/4320/
- new mission system "Sim Director"
Completely new scenario editor. We'll see how it goes. See
http://www.prepar3d.com/news/2013/10/4561/
- new multiplayer code
Read something about it, but can't remember nor find it, so
IMHO the step from FSX to P3Dv2 is anything but "just cosmetic". For me it is the step to FSXI that never came.