Hearing that it's the LUX with all that you had listed, I would tell you that it's a very, very good price! We spent a few months checking out the '07's and we were very good at negotiating.
No one came near the offer you were given on an '07. We were offered similar to what you're looking at, but without a sunroof, brushguard or step ups .. for $49,900. One last word .. check the build date (out of curiosity), the tires and the battery. Actually the build date would tell you how long it was standing. After being on this forum for awhile, I got the sense that folks getting vehicles sitting on the lot for awhile had some issues with the tires and battery. THEN, hit them one more time with one last lower offer. I think the offer now is great. Keep in mind that the Hummer dealers are a little hungry now for sales since fuel prices went up. We shopped six dealers .. all said sales were way down. Perfect time for a Hummer lover to get one, in my humble opinion.
Good luck and tell us if you got it!