I love the clean lines and straightforward, Teutonic styling on my E53 (2006) X5. However, compared to the E70 X5, it is a noticeably older design.
High quality interior materials. There's soft plastics almost everywhere, which is nice since we used to only have Japanese cars. The buttons and knobs all feel very solid.
This X5 handles much better than any vehicle this tall should handle, with just-right steering, good brakes, decent composure in the curves, and excellent straight line stability.
Because it's so tall and because it's shoulder-line is relatively low, there's excellent visibility out front and out the sides, and decent visibility when backing up.
While I wish the 3.0L i6 had 50 more ft-lbs of torque, it does fine even in the thinner air of Colorado. The AWD system is amazing in the winter, and combined with traction and stability control, makes the X5 a very safe vehicle.