I got my first diesel in 2006 and it's a GMC 2500 and I like it. Bought because of things I read about diesel trucks that can be made to produce more power with a plug in tuner. The price of diesel was reasonable at the time.
I don't use the truck often, only going to the range on Sundays so it only has 21,000+ miles on it. I did buy the extended warranty after hearing how much these things cost to repair. That was a waste since I put so little miles on it.
However, my brother bought a used 2005 GMC 2500 since he always wanted a diesel. His truck had about 71,000 miles on it and he bought the extended warranty. Soon after he bought it, he had to replace the idler and pitman arms, the door latch switch and something else. All those repairs would have cost more than what he paid for the extended warranty.
Me, my truck needs the door latch switch since the dome light does not come on when I open the door. It cost me $218.00 (that is just for the part as I will install it myself).
Check out prices for filters (oil and fuel) that you will change often, some guys buy in bulk to save money. Oil will be costly (I need 10 qts) especially the synthetic stuff. I use a Power Service Diesel Kleen additive to keep the injectors lubed (this can cost in the thousands if they have to be replaced). Knowing this, I tend to take better care of my truck.
I keep a spare fuel filter in the truck in case the one mounted has problems (clogged, leaking) as the injectors don't like air.
Be prepared to pay some bucks for bigger repairs if you can't do them yourself. I still love my truck but probably would buy a gasser if I did it all over again.