That all depends on how much I will save. If it is only a couple bucks on a $100 item I will almost always pay more for better service. It also depends on how much service I would be sacrificing. I do tend to be fairly loyal and once I am happy with a store it would take quite a bit for me to change and I would have no problem spending a few more dollars to shop there than somewhere else.
I go for the customer service if its within 10 buck or so. But if its a 100.00 I would go with who has the best price. I am generally faithfull to a store when I buy something if they have good customer service.
Customer service consists of knowledge of the product, knowing the customers name, smiling, and a willingness to make something right if its not right.