I think Hummer tells the story of what is wrong with GM. Instead of making these niche vehicles a model under an existing make (GMC, Chevy, Cadillac, whatever), GM made Hummer into its own brand, with its own dealer network (and expensive buildings). Now GM can't axe the brand without paying off these dealers.
Hummer did come to this (now almost dead) market first, and they changed the market. Look at the Jeep Commander styling and the FJ Cruiser for Hummer-inspired themes. Hummers are reliable, capable and stylish (although to many, not their cup-o-tea).
My opinion (and I'm a died-in-the-wool GM fan), is that Hummer was a fantastic idea, done wrong by the idiots at the RenCen. For these and other stupid ideas, Wagoner should go. I just hope GM gets back on track so I can buy their stock. My next vehicle will be a GM truck.