i have a 08 duramax. i love it as well. i have had no trouble with it.
the newer ones dont get as good fuel milage as the older ones. my 02 duramax was got about 1 1/2 mpg better than the current one, thanks to emmisions. but i didn't buy it for fuel milage.
i had a 05, f-350 ford king ranch with the diesel in between. i did not like that truck at all. it was more me and the cab comfort of a chevy, not saying ford was a bad truck, just that i didnt like it. it rode rough, and was not good off road, mostly due to the stiff suspension. seemed like i had to put it in 4x4 every time i turned off a road.
the duramax is quite and powerfull, the allison tranny is a nice compliment as well.
by the way, the new diesels will have urea (sp?) injection and a whole new emmisions package.