A bud of mine has a 2012 Duramax deleted. We use it to go snowmobiling in the rockies in winter. It gets much better mpg deleted. Other than that it is really no noticeable difference in running and driving. The truck is probably the opposite of a fire truck. Its main use is interstate towing a light trailer. Very little city or idle time. He did have a sensor in def tank go bad, and I think a NoX sensor go bad as well.
Note, the exhaust is louder than stock. He left the Cat on and bought a quiet exhaust. Its not loud by any means, but its still louder than factory. Not loud enough to be annoying, but driving for 24 hrs straight with loud exhaust is not cool. Just a FYI.