I have 400k plus on my 07 Hino - and have had only minor problems.
Its not underpowered. If you're bogging down in the hills try, changing your fuel filter.
I popped a head gasket about 50k miles ago. Which I brought to the dealer the day the warranty expired. Hino corporate covered the repair, and even sent a corporate TECH out to inspect the engine, according to Rush in Fontana popped head gaskets are rare with hinos.
I suspect I popped the Head Gasket pulling the grapevine with a load during the summer, I stayed in it and let it run into the red like a retard.
All in all I have spent more money repairing my APU, than my truck.
Yes they can be in-framed.
I get about 10 MPGs now that I have slowed down to 58 mph.
I have a gulfcoast oil filter, (single element) which is nice, I change the filters myself, which helps keep untrained monkeys off my equipment.
It seems the more work I do on the truck myself, the less problems I encounter. Same with the apu - since I stopped taking it in to carrier, it seems to be more reliable.
This should be a general lesson to all owner operators. Mechanics don't give a rats *** about your equipment. If you don't do as much of the work yourself you'll find your mechanic will create as many new problems as they fix.