Enjoy reading the comments and want to share my own experience as well. I just traded in 2010 X35d with 143k miles. The X5 had been great to me with exceptions of few emission related issues (EGR coolant, DEF tank, metering unit) The dealer was great and even took care of some of the expensive repair under warranty beyond the warranty period (replaced the DEF tank sensor and pump around 100k) Although the car still drive great, one of the main decision was the up coming repair quoted by dealer when car went in for 135k service. I was quote almost $7k of repair for DPF (diesel particular filter) and battery change out. I am also coming up on the front brake and rear brake (on my 2nd set on both). Need new tires and drive belts are still original.
BMW dealer appraised my car at $12k, so didn't seem logical to spend more then the vehicle to keep the car going. I was told by an indy shop that I should budget for transmission rebuilt or replacement as well.
Last minute decision and had purchase a new car before end of the year, so my option was kind of limited. My list was short - Another X5 35D, X5 35i, GL450, or GL350 BlueTech. Went to test drive all and had decided on X5 35i since I don't drive as much any more (went from 120 miles commute/day to 30 miles /day)
I couldn't find one with color and options combination on the dealer lots beside the BMW dealer was only giving me $12k for my X5.
On the last day of the year, found a 2013 GL Bluetech at local auto wholesale place where I had PermaFinish done on our company vans. The GL has all the options I was looking for with low mileage. The car was in almost perfect brand new condition. The dealer gave me $15500 for my X5, so I went with the trade.
My plan was to drive the GL for a while, if I don't like it, I can order a X5 and trade it in.
Now I had the GL for few days.. It started to grow on me a little. GL doesn't handle like X5, the navigation interface and iDrive on the BMW is way better than the MB, but the GL is more luxurious and feels more compliant. I do use 3rd row some times so GL 3rd row is more functional.
If anyone interested, I will report back again once I have the GL for few more months.

Chao.