I have the SL65 too. Lots of power but not much problem with ending up sideways. The ESP kicks in and takes control of any slipping very quickly. Also, if your in CT, then it has been freezing here. I'm in CT, and the temperature is rarely above 32F this time of year and there is lots of snow and ice around. The tires are not great in this weather and run much better on a surface with a reasonable temperature (warmer). better grip in in Spring , summer or fall day.
I just put mine in storage for winter because the salt, sand , snow and ice is really not good for such a quality car that is so low to the ground. pebbles, sand and salt are always being kicked up from other cars and constantly hitting other cars. Often,too small to actually see but when you have a car this low to the ground, you can actually hear the sand and salt hitting the body of the car. I just dont have the heart to take my car out in this kind of weather. I treat it with a lot of care!
On the other hand, maybe your freind just needs a bit more practice driving the car so he doesn't over-do it. It took me about 1-3 days of driving to get used to the power of mine. I want to let my wife drive it in the spring but am reasonably cautious as I know if you are not very attentive at 1st, and dont have any experience driving a car like this, then you could end up hurt or worse. So, I will be a bit nervous when I go on my 1st drive with her at the wheel. She seems to be confident though. I had a 2004 E55 and she did well with that car. The E55 was a lot more responsive, agile and quick on the takeoff though. The SL65 is a monstor though once the wheels are moving.
The awesome feeling of the tourque is wonderful though!