[HummerJim]

The engine, transmission and many other parts are shared with other GM products. You're probably going to need a new windshield now and then too. There are enough H2s out there to make getting parts not that big of a deal and it looks like they are going to start manufacturing them again anyway.
As for mileage, it's not much different than what you'd get in a three quarter or one ton 4 X 4 truck and most Hummer owners consider the gas a small price to pay for owning a Hummer. As for other people's opinion, you're going to hear anything from Yuck to Awesome, but I bought the H2 for me not them and I love every minute of driving it. If you own an H2 you'll never go anywhere unnoticed and people you've just met will offer their opinion on Hummers - except for my Corvettes and when I had my XKE, I've never experienced that before with anything I've driven. People are going to comment on your Hummer all the time. My sister-in-law thinks it's the ugliest vehicle ever made, while my grandsons think it's "the most AWESOME vehicle on the planet."
Five minutes offroad in the mud or in deep snow and you're going to be so glad you have a Hummer. They have the fastest and hottest seat heaters of any car I've ever owned - important in the winter and with my trick back I find myself in the parking lot this time of year sitting in the seats reading with the seat heater on while my wife is in the mall shopping. After all these years it hasn't gotten old driving it and I don't feel that urge to trade like I have with other vehicles after a few years. My biggest inconvenience is that it won't fit in the new parking garage when I go into the city for baseball games.