I have. Its fine as long as you know what you are looking for, know what goes with what and what should not go with what. The folks at my PetCo simply are not familiar with Cichlids so they could offer no helpful advice. They do sell NLS, though.
Edit: Let me elaborate a bit. My I purchased my first Cichlids at PetCo a long time ago, having no clue how complicated it is to keep Cichlids or that forums like this even existed. With their advice, I purchased a Yellow Lab, an Electric Blue Ahli, and a Tiger Oscar. Anyone with any experience whatsoever will laugh out loud at that combination for a variety of reasons. Now, that being said, their return policy is unmatched, and they have a very friendly staff. They also openly admit that they are not experts with Cichlids. I'm a big fan of shopping local, so I do shop at both PetCo and PetSmart when possible, but I do my own research first. The best place to do your research is this forum.