The situation with the rifle above is the absolute worst case I've run into in 10 years. It was worth what I paid for it just to see it for myself. I eventually sold the rifle for what I had into it to a friend of mine and he's enjoying it immensely.
Pro's:
The C308's are very nice looking rifles with the PTR receivers (professional looking welds) and nice paint.
The original components of a Cetme are mechanically (metalurgy, hardness and finish) identical to HK components - better than PTR parts.
Properly assembled with serviceable parts they will run along side of a real HK91 shot for shot.
Con's:
Bolt carrier groups come from used military rifles. Condition is luck of the draw with what you receive.
There are no NOS replacement parts (at least very few) such as bolt heads and locking pieces.
CAI's piss poor Cetme builds prior to 2010 gave the Cetme name a bad reputation.
PTR rifles have their problems too, their customer service/repair department works very hard to keep people happy so the problems fade from memory quickly. They have the advantage of parts interchangeability with HK91's. I've lost track of the number of times I've read that owners replaced the PTR internals with HK parts just to "improve" the rifle (probably just for bragging rights).
I have one HK33 clone that I built and an HK91 parts kit sitting in a box. The rest of my DRLB guns are Cetmes in different configurations and calibers. Here's an old pic of some: