Honestly I know it's not that new or special but I regret my 2010 Ford Escape that I bought "low mileage" in "good condition" from the Ford dealer and wish I'd just stuck to my cheap cash trucks... My Escape been totally reliable with no issues in the last 50K I've put on it (it's got a bit over 100K now) but it's just not nearly as enjoyable to drive as my Suburban and I hate having an (albeit very low) payment on it.
The 01 Suburban I just bought is the 1st GMT800 I've ever owned... about 290K on the clock, yet I trust it to start every morning and if someone gave me an unlimited gas card I'd drive it across the country with no hesitations.
I've owned many GMT400 trucks, some Suburbans, a Yukon, and a few pickups, but the GMT800 really is a step up in terms of handling and refinement. So while both generations are fantastic the newer ones are definitely better daily drivers.
I think if you have a well taken care of, rust-free 01-06 GMT800, hold on to it! If properly maintained and not abused, 200K+ miles is irrelevant. I work in the automotive industry and the 07+ trucks are nice but nowhere near as reliable or affordable to keep on the road. The new tech is nice and the newer ones get better MPG, and in theory they are safer, but at the end of the day, nothing wrong with keeping your GMT800.
With gas prices being the way they are in the SF Bay Area I know I should be driving my 2010 Escape not my 2001 Suburban but guess which one is parked behind work blocked in by a bunch of pallets and which one I get into every morning?