Of all current Mercedes platforms, the SL has by far the best chassis, with the best steering and handling. On a familiar track, the SL55 is so well balanced and natural feeling that it nearly finds the smoothest line by itself. And it has 493 bhp, the sound and thrust of the engine combining for a sensually rich driving experience. I would not normally be bothered with a 4,280-lb two-seater, but the SL55's dynamic excellence won me over. Thus, I had high expectations for the SL600.
One passenger commented, "Yup, V12s sure are smooth." That's good and bad. Whereas the SL55's symphony encourages smoky shenanigans and cheesy Wagnerian mental soundtracks, the SL600's engine emanates little more than a smooth, vaguely mechanical whirring. As the luxury model, its exhaust is well corked. Not that it is underpowered. Flooring the happy pedal for onramps typically results in exceeding the speed limit by about 50% before merging. And the car is smooth at such speeds. On a perfectly straight, perfectly empty desert road, a little autobahn simulation surprised me with how quickly the car pulled well past the speed where the last powerful car I had there was shaking and jumping around. As on the real autobahn, I found being along for the ride at such speeds strangely unexhilarating. I prefer to dance.
Driving one of the best roads on the planet, I felt committed to decisions at lower levels of cornering effort ("tenths," if you will) than in other cars. The sensation was that the SL's vast mass would make changing my mind about anything a significantly longer process than in smaller, lighter cars. When you don't know there won't be rocks or sand in the road, and you don't remember every single turn's line to the inch, it's hard to be serious about speed in a car such as the SL.
I have decided I don't like Mercedes' electronic braking. Around town, when efforts are low and modulation careful, one sometimes notices that the brakes aren't doing exactly what one's foot is. In the mountains, it became obvious. The most notable discrepancy was in release time. A short dab of the brakes to check for their continued effectiveness and settle the chassis always lasted longer than I asked. When the road went downhill for several turns, the brakes lost effectiveness. I'm allowing that it may have been green fade on 1600-mile pads, but the electronics didn't seem thrilled. I was surprised to find the pedal feeling longer; I don't know whether the force resisting my foot actually decreased, as with boiling fluid, or if it was the reduced friction making me have to press farther to get the electronics to squeeze harder. In other situations, it seemed the available braking levels were almost in steps. On a freeway offramp, I increased pedal force slightly, got more slowing than I had wanted, backed off a little, got what I had had before, and repeated several times. It was annoying, and disappointing in a car of this price. I've noticed similar discrepancies of finesse in the electronic brake response on the E500 as well. It's possible the average SL600 driver won't notice such things, but I would think any AMG driver would.
I've said before, and trust I'll say again, Mercedes has the best automatic transmissions in the world. Given time to adapt to an individual's driving style, they work as well as one might think an automatic can, even with just five speeds. The shifter's manual function is simple, always ready and more intuitive than any other.
I turned on the navigation system, and couldn't turn it off. The manual was not in the car, but I chased down every menu in the navigation system without finding the "Piss off, eh?" setting. On the phone with the Mercedes specialist at the fleet management office, the menus he described didn't match what I saw, and I randomly pressed a button that worked. I never did figure out how to make the "speed volume" function go away. Clearly intended for use with the top down, its effect was far too great with the top up. Not even the fleet specialist could help me find a way of reigning it in.
The power seat adjusts every which way, and even has a moving lumbar support "massage" function. I never was able to make it as comfortable as a really good ordinary seat, but the moving lumbar at least made sure it wasn't wrong the same way long enough to become really uncomfortable.
The SL is Mercedes' technological flagship, with all the technology and features it could figure out how to pack into a two seater. In certain ways, it seems Mercedes is pushing the envelope of its own capabilities, and the very few imperfections are made more prominent by the overall excellence of the vehicle.
Here's my bottom line: I believe the SL55 will do luxury just as well as the SL600, but it will do much, much more. The SL600 is a nice guy in a better suit. The SL55 is a werewolf in London.