I bought my '95 with a 79C thermostat, always held there, didn't notice any problems at all. I recently replaced the water pump, and while in there, my t-stat with the 87C that the car calls for. Temps are steady, no problems at all.
The only thing that makes me alittle concerned is that with the 104 motor especially prone to overheating damage, I was alittle more comfortable when the engine ran cooler.
1995 E320 40K
1999 Tahoe 90K
2002 JX8 Sport 43K
2005 Volvo s40 65K