I don't have any diesel specific experience with these types of IC's, but I have worked on them in turbo gasser applications.
Benefits:
Less pressure drop (there's usually a smaller core that the charge air goes thru... )
Ability to have LESS THAN AMBIENT air temps at the intake - with gassers, this helps to make a boatload of power. With air/air IC's - it's kinda hard to get below ambient air temps without some form of external cooling - water spray or even carbon dioxide, nitrous oxide, etc...
Drawbacks:
More plumbing - you have to run coolant through 'em AND you still have to plumb them up like a normal IC
More (moving) parts - you need a separate pump, heat exchanger, lines, etc.
There are some good buys on air/liquid IC's on eBay... look around. I'd use 'em on a drag race or sled pulling vehicle... you can ice down the coolant between runs, etc. For a daily driver, air/air works just dandy and is the least pain-in-the-neck way to cool down charge air temps.
Matt