The good: Cheap engine, decent fuel economy when set up correctly, start ok when cold, will burn anything that does not explode, they will keep a trawler from moving due to wind (make good anchors).
The bad: Oil leaks, low power (even turbo'd), hard on transmissions, difficlut to tune correctly, go to "WOT" if the govornor sticks or you set the hand throttle, "V-8" GM diesel, loud, difficult to repair, parts varied a lot.
The Ugly: They EAT headgaskets, crack heads, injector tubes leak (fuel in coolant), when they break it is terminal, the cylinders FLOAT in the block!, few people WILL work on them - only the looney.