I love the GT even in 4.2 guise... but what I have seen and know from those in the trade is that they do not wear as well as the coupe due to having a 2 year service scheduled and a harder initial life as well as a less sympathetic owner group.
For many cars the two year interval is a misnomer as the autos are bought to be used and the cars often get to the 12.5k mile interval before two years is up. Anyway Porsche has existed for years on 19k/2 year and, yes, we read about some issues but they are not the norm.
I guess as the buyer group widens then many owners will see them as a three year commodity but that makes Maserati try harder and means they must adjust to the reality of what the likes of BMW have operated within for years. The Ghilbi will further develop this.
These cars are reliable though. Mine is 4.5 years old and is on 33k miles. The only warranty claim of any merit is a new a/c compressor.