Did they use brake lubricant and/or shim them properly?
I haven't needed to do my Altima's brakes yet but I know this is a common gripe and it's an easy fix. $1.50 for a pack of brake lube. Just follow the instructions on the pack.
Did they use the cheapest parts with the highest markup?
This happened to my parents. The brakes were fine, they just squeaked from day 2.
As a sidenote, you'll save a bundle doing your brake-work yourself. If your getting them serviced at a dealer you're paying (no exaggeration) about 10x what you'd pay yourself. I'd spend $550 getting my brakes done by my mechanic until i took the initiative and learned how to do them myself. The same work cost me $60 3 years later.
