For what it's worth, I've dealt with ARA several times now, and so far each time has been a good experience.
Before I send in anything, I try to verify the purity and record the weight of my finds.
The same can be said before I buy any jewelry, I check it out carefully.
I use a 10x loop, a strong rare earth magnet, an acid test kit, and later I got a GT-3000 electronic tester.
ARA has always sent back any stones, and I've not been disappointed in the payout.
I sent ARA some gold filled items, and they even sent back a baggie of the non-precious metal core pieces that didn't dissolve. One example was the upper portion of a vintage class ring which had tested out at 9K. This is very helpful in my opinion, because it shows me that they extracted and paid for all of the gold - I can deduct the weight of the returned junk metal and calculate that I was paid properly.