It is a great chassis with the GM 8.1L engine and the Allison transmission.
There was a brake recall several years ago that should have been completed on any existing chassis three years ago.
Depending on which year you get it could have the grade brake on the transmission and it could also have a double overdrive gear ratio, which when coupled with the right rear axle ratio allows you to climb the Western mountains while towing and passing most everything in the right lane. The double overdrive also allows you to get reasonable fuel mileage if you think 8 MPG is reasonable.
Parts for the GM 8.1 are available at any auto parts stores and most any mechanic is familiar with the engine. The Allison transmission is bulletproof.
Workhorse parts are still available but most any parts you need are available from alternative sources at a lower price.
With reasonable care they are rated at 200,000 miles.