Your computing environment is not Turing complete either! Here's proof: while (true) { print("hi") }
Run that, I guarantee it will be interrupted because it used too many resources. How long will it be before it's interrupted? Well, that can be arbitrarily long. But it's the same with ethereum. There won't be any infinite loops that don't get interrupted after some reasonable time.
Whether new nodes having to catch up by executing a billion scripts is a problem, depends on whether the history grows faster than Moore's law. Hopefully there's some kind of feedback mechanism that prices ether according to computing power needed to operate a full node.
a 'computing environment' is not Turing Complete, but computer languages are.
this poses the first problem of FALSE ADVERTISING. These aren't Turing Complete scripts, it's just a bloated up dispatching environment for financial transactions. I think they're overestimating how 'cool' this is going to be. It's not going to be fun to make or to use. Why dont they just use the JVM? you can control thread execution from another process. Java caught onto CLLs long before these guys declared they discovered the idea.
there is an entire field of research called 'workflow engines' that attempt to deal with these problems. If you've ever worked with one, you would probably come running back to all your Bitcoin friends after a few hours of mind numbing process definition languages and the like.
if they can make this as advertised and it's open source... great! have fun storming the castle!
-bm