I have had both good and bad with J&M. Nice selection, but pricey, though they do have good prices on accessories (quadrum holders etc...).
I did an order of common coins, and one came with a big fingerprint on it, I have seen their staff in the store handle coins raw in hand, so not surprised. Coins were all packed in envelopes, did not see it until I got home, a $6.00 purchase, so not worth the time to phone/argue.
I've sold a bunch of junk silver and bullion to them, good prices and pretty seamless.
Their new location is a hot mess and work in progress. Stuff everywhere, staff don't really know what is going on and active construction site. Unless you really need something from them, I would wait. Was not impressed with my last visit, poor service, disorganized and not planning to visit again soon.