I am also in agreement with BenjaminNYC on this one. I will fill out the GTEM cards and have dropped emails before on good service, but that is as far as I will go and the service has to be great. Otherwise, rewarding mediocrity does more damage than good. Think for example of the waiter or waitress that becomes accustomed to a 15% tip and I have had it where a waiter has come complaining to me about a $1 tip when the level of service was horrendous. I certainly believe in tipping where due, but I will always make sure that the tip is in line with the level of service received.