Spoke to a colleague within Delta who claims the company are very disillusioned with the performance of the 76-400.
Plans for the aircraft included ATL-HNL non-stop this winter and ATL-GIG and ATL-EZE non-stop from the spring.
It's cost Delta a small fortune reassigning the aircraft onto the LAX and SFO-HNL services, whilst ATL-HNL is back to the good ole L1011.
Couldn't get anything more specific performance-wise out of him, but hope this helps.