MBW- Agreed x10. In my experience, if you run ANY liquid cooled engine out of coolant, you have about 30 seconds before bad things start happening. I don't care if it is a Ford, GM, Toyota, or Land Rover.
Does this engine have annoying weak spots? Yes. Can it be a pain in the ass to work on? You bet. Nonetheless, I challenge the OP to drain the coolant out of his Suburban, take it for a 2.5 mile drive, and post the results on the Chevy forums.
I imagine they will be much less constructive than we have been so far.