I've just upgraded my cluster from 5.5.2 to 6.0, and found that some code I was using to bulk index documents just failed. After some digging about, it turns out that I was doing two bulk index operations - each one storing a different type, both to the same index. This worked fine before, but due to the new limitation that an index may only contain one mapping type, the second op was failing.
The big problem I had was that this took me much longer to diagnose than it should have done, because NEST v5.5.0 just returns the debug information with a System.NullRef exception as the error message. There's no useful diagnostics whatsoever to hint as to the problem.
When do we envisage NEST v6.0 coming out with better handling for this situation?