The other typical drawback of giant rims - massive unsprung weight that makes it feel like the suspension is possessed by the old Tacoma Narrows Bridge - is averted by the GL's air suspension with adaptive damping. This system just doesn't seem to notice that it's slinging around wheels that each probably weigh as much as a Viking range. There's a bit of head toss typical of a high-riding SUV, but on the highway the ride is serene enough that if you got pulled over for speeding, you could quite truthfully argue that you thought you were going 14 miles per hour.
Besides the rims and the motor, the GL550's main calling card is its grille. It's more upright than that of the GL450 - more brash and in-your-face - and adorned with the biggest Mercedes badge not affixed to a 100-foot-tall fluorescent sign outside a dealership. Certainly, nobody will see you pull into the driveway in the GL550 and ask, "Oh, my, I wonder what kind of car that is?"
At $78,200, the GL550 demands a $21,475 premium over a base GL450. However, as near as I can tell, when you option a GL450 with all the stuff that the GL550 includes as standard - navigation system, 11-speaker stereo, heated rear seats and on and on - the price differential falls to something more like $9,000. However you look at it, the GL550 is priced just about on top of the Range Rover, providing a high-tech, street-oriented Teutonic foil to the Range Rover's old-school gentleman's off-roader.
The GL550 is fast, expensive and luxurious, but so is the GL450. What sets the GL550 apart is confidence, perhaps even arrogance, in its mission. This is what an $80,000 Mercedes 4x4 looks like. Deal with it.