I don't know about the reviews but I own a 2008 Expedition with a 6.7 ISB and a Allison 3000 trans. I purchased it in 2009 with 4,000 miles. I do all the maintenance myself except one software update at Cummins.
I now have almost 70,000 miles which included a 14,500 mile Alaskan trip.
I have been quite happy with it. Sure I have had minor issues, but nothing that really pisses me off.
Earl & Sharon, 2008 Fleetwood Expedition, ISB 6.7
1995 Jeep YJ/2013 Chevy Sonic