We'll just leave the whole Toyota debacle behind us.. I agree, the 5.7 and 4L80E in your Sierra is bulletproof, love that truck.. Oldman has a '07 Duramax with the Allison tranny, doesn't complain regardless of what we hook up to her..
I still haven't found anything that's come close to lasting as long, or gets the mileage my TDI does. My last Jetta had 600,000kms on it before I retired it to pick up my '05 Jetta TDI Wagon which currently has 330,000kms on it. For a daily driver, it's the only thing I'd buy.