Just thought I'd throw my 2 cents in here.
If you are going to keep it for a while (4-5 years), go for the '06. If you think you'll want something else in 2-3 years, go for the '07. Depreciation will still hit you pretty hard, but not as bad as the '06.
GMID minus the incentives is a pretty good deal (at least for those of us who paid MSRP because the trucks were so new and hot). Still worth every penny.
If you aren't that comfortable with negotiation (or just don't want to waste the time), bring out the GMID upfront and save the hassle. Try to avoid playing the games the dealers sometimes play and be straight with them from the start. You may not get your "best deal", but at least no one will be pissed off and you may be able to build a relationship that'll pay off when you buy your next Hummer.
By the way, 15 months and 30k miles into mine I still grin every time I walk out to get in it. Get one and I'm sure you'll do the same.
Good luck!
