There were no revisions of the NEX1500.
I know personally people who run them and have no problems at all, and use them HARD too.  There was some ripple on it, that is true, but it was well out of the danger zone.  They were more of the nothing fancy work horse, think like a diesel engine in a semi, might not be perfect of efficient, BUT it is a strong competitor and in general (I know some people have had issues) pretty solid and reliable.
 
Now, that being said, the 1600 is a better unit all around.  It's just that simple, 1600 is awesome.