[Macca2801]

On its own the engine is probably the most reliable part of the Jeep.

Needs good airflow so as stated keep the coolers clean and dont restrict airflow with large spots/winch boxes etc.
The boost hoses were changed from about 2009 onwards, but either way...factory hoses dont like oil and with out blowby fitering they will degrade. So either fit a Provent or the Samco silicon hoses and you should be sweet.
No clutch issues with the auto so thats a bonus.
The way the engine is fitting in the engine bay can be improved with a few Zip ties and spiral wrap. Look for rubbing A/C lines, P/S hoses chaffing on boost hoses, and wiring looms not as secure as they could be.
I spent 4 hours cleaning all this up within a week of purchase and had already found chaffing and wear in a few places.

Long term reliability "should be good" there are a few JK owners hitting 100 000km plus with no engine dramas and I look at the KJ owners with the earlier 2.8 for optomistic reasurance. They are still relatively young in the JK but it looks promising.

For a quick rundown thats all I have, love my CRD and intend on keeping it long term. Hope this helps.

Matt.