Just for clarification do you mean a Coupe GT, or a new Gran Turismo?
If you mean Gran Turismo, I doubt 120 miles will be an issue. They've worked on this car for a long time, and I believe they did a good job ironing out any bugs. Keep in mind there are waiting lists for the car now, but very few if any customer cars have been delivered stateside yet. We should have a better idea of any quirks in the near future
The SL is a fine car - better than the Maserati in many ways. I've had two SL500s before a 4200.
Maser is a much busier drive - gear ratios are too close together - steering overly sensitive - footwell a bit cramped and build quality a little dubious by comparison. Scuttle shake is very bad on the Spyder next to the SL.
However it's gorgeous to look at, the engine is sublime offering greater performance and aural delight! It's nice to be a bit different (brave?) .