I had an 01 Yukon XL we purchased with 70K and drove it to 330K, both my boys learned how to drive in it and we took many trips across the country in it. I then used it as my pickup truck until we sold it to a neighbor who is still using it today. We never replaced the transmission, but did replace the transfer case once, a bearing went bad on the inside and beat a hole in the side of the case allowing all of the oil to leak out. Other than that, there was general maintenance along the way and front and rear main seals as well. It was a beast and we loved it.
I now have an 05 Tahoe that is my daily driver with 154k on it and going strong. When I purchased it, I put around $2K in it doing a lot of what everyone else on here has said, I did new brakes and calipers, upgraded the fronts to the GMT900's, new pulleys and belt, some AC repairs including a couple actuators in the front and back, new shocks, new hoses, new steering wheel buttons (just to get the backlights working), new radio face, new driver seat bottom, WeatherTech floor mats, paint correction, painted the dash, etc. But now I have a very nice daily driver that should be good to go for another 150K, and all less than $10K. I don't think there is a better SUV value out there because they will run forever and parts are cheap...
I agree, the older ones are less electronic, but are getting harder to find a lower mileage one. I personally like the 05-06 models because they had conveniences like steering wheel controls, triple climate controls, heated seat backs, turn signals in the side view mirrors, adjustable pedals, etc.
