If you establish a relationship with a person at said shop, your choice, the relationship should nurture future bike purchases. While I agree a shop should have a level of service to keep everyone happy (customers new and established) my best experiences have been when I do business with people i know. I still make bike purchases and get recommendations and opinions from someone I met 17 years ago in the bike business so don't have the same disappointments of others.

I have also not hesitated to express frustration when not treated as expected or anticipated as they can't fix what they don't know. Knowing and not fixing is another story...