I have the 2nd generation LLY Duramax engine in mine and i love it. I had to replace the injectors when i bought it at 130,000 but other than that i have just been upgrading. The ride is great, the seats are comfortable, the fuel economy is good, 20-24 highway, 15-18 city, if i keep my foot out of it(hard to do with 400 HP and 600LbFt of torque on tap). I have not had any major breakdowns since owning it. The transmission did blow up at 143,000, but it was a freak electrical short that caused it to engage 2 gears at once(lots of chunks in the pan). It actually got me all the way back to the shop in limp mode which was about 25 miles, 10 of which on a logging road.
The Duramax engine, the cab room(front and rear), easy to work on, good mileage,the lighting(upgrade to a Bright Box)it is good stock though, handles great in all weather, the ride is great and the in cab storage is very well thought out.
upgrades the tires to 33"(no lift required), upgrade the headlights with a Bright Box, aluminium skid plate are far better than the plastics(get some) and some step bars so you dont destroy the edges of the seats