I tried the demo the other day as well.
This is the conclusion I came to.
a. It looks better then the default version of KDEN
b. The performance is pretty good, although when the buildings aren't blinking in and out in the demo, it migh be worse
c. The airports photo real textures blend pretty well with MegaSceneryEarth Denver area summer textures and night textures. Of course since MSE has no seasonal textures, it might be advisable to disable MSE when you fly there in the winter.
However the bad part is:
a. The runway and approach lights are HORRIBLE... When your about a mile or more out they look like one solid light. In fact, I think I heard that if you did some of their latest updates, like the update to KATL for example, you would be left with these horrible looking lights. Ugh.. too bad they couldn't have done something else about this part. Glad I never did run the KATL update if that's the result.
b. A little bit of extra work might be needed to clean up a shimmer here and there, as well as convert some of the textures to DXT w/mips to improve performance and looks. I didn't bother with that since I just tried the demo, but I would imagine the sale version uses the same textures.
c. The textures, namely the taxiway and apron are pretty bland, the runways aren't too bad, but its not as good as FSDT or FlyTampa puts out. The buildings are the same, not blurry, but just bland looking.
Overall, it's not too bad, but I think I am going to wait a while on this one. With FSDT posting some new updates for KLAX this evening that make it look like its almost done and PMDG finally wrapping up the NGX, I think I will save my pesos for now and use them on those products. At some point I will probably get KDEN, but its not an airport that I am really interested in that much to spend $30 on at the moment. I'll save it for one of those days when I am bored and want to buy a new airport.
If I was going to buy it, I would be sure to do it via the Flight1 version so that I could get a refund if the paid version performed worse than the demo version.