my 6.2 with a banks has been pretty good for its 194k miles. it can be a huge pain to work on, everything is packaged in an unfriendly manner. for example the factory passenger side battery is a side post case, and the turbo airbox wedges right up against it, so getting those teminals on and off sucks, i eventually went to a top post battery there. there is a cross over pipe that runs from the drivers side manifold to the turbo, that thing is in the way of just about everything, the fuel pump, the bottom coolant hose, and numerous other things i would like to get to but can't with out pulling it.
All that headache fades away when i drive it. I love the mileage Ive gotten 21 mpg with a leaky injector. The power is great for most 4 wheeling i do, its smooth, easy to control, it has gobs of the right kind of torque right off idle, which can make anyone a hero in technical sections. the only place i wish it had more power was hill climbs, but keep in mind this is from the mouth of a 20 year old who also rides dirtbikes, so if i had to guess its great for most people. I also like having the unique and cool factor, i always get asked about it which seems to have been a good way to meet others like us.
so bottom line, its far from perfect, but overall its worth it.
--Scott