I am not sure what you guys are whining about, but I have spent probably 10 Januaries in Buenos Aires, and found it refreshingly uncrowded, and, sure, a few restaurants were closed for the month, and, there was definitely a lesser amount of concerts and nightlife, but I never have had an issue getting anything, food, services, or shopping. There are still a half dozen verdulerias and ferreterias within 3 blocks of my house.
My experience with customer service has been its always good with small family owned businesses, and crappy with companies trying to be modern and international, trying to emulate US or Euro chains.
I know most of the people I buy things from, the guy who fixes my watch, the lady who resoles shoes, the chicos at the hardware store, the fruit stand and the egg guy who deliver. Their service to me during the holidays is exactly the same friendly service I always get. It helps that I talk to them, get to know them, and am a repeat customer.
I really love walking around the city in January and early Feb- its a great time to really see things without too much traffic or hubbub.