It has very little to do with the "engine" being bullet proof as much as the fuel delivery side of things being "bullet proof"

The mechicals of the engine don't care to any large degree due to the fact that fuel is fuel. The IP and injectors on the other hand are the ones having to test their durability. I think as long as the technology behind handling the actual fuel itself doesn't change (compared to the more robust older engines) much and proper filtering/fuel switching is performed, you won't have any problems.

When the technology vastly changes (like CDI engines) then you have bigger issues starting to worry about

I won't touch the Chrysler issue...my friend works for a dealership of Dodge/Chrysler and any day of the week I can get into an argument with him about cars. Though we both agree, MB and Chrysler/Dodge have gone to hell.