I've made several purchases at Joe's over the last 8 years, always from Jack and Sam. The 66 Front Street store is smaller than the "main store" but they can help you shop the other locations as well. I've had each piece of jewelry appraised by a professional appraiser (he does not work at a jewelry store and is paid for his time). Sapphire pieces appraised well compared to what I paid while diamond pieces were more "break even." The stones and metal were as they were represented to be.
I've enjoyed my visits with Jack and Sam, have had no complaints, and have recommended them to friends. That being said, when making a big purchase you need to do your research to have some idea of fair pricing. It's easy to do on watches or designer jewelry styles. For other pieces, ask for a loupe to look at stones yourself for obvious flaws.