I returned one of my two note 3's to TMO for a replacement due to a cosmetic flaw. It was Knox tripped. I had no problems at all. I did unroot and factory reset before sending it in though. replacement shipped same day and arrived the next.
I left my second line Note 3 on top of my car and drove off. It had a Spigen Slim case on it and stayed on top of my car till I had to brake for a yellow light. The phone landed 5-6 feet in front of my car and the screen cracked. This one was Knox tripped also, and I didn't bother unrooting or resetting it. I sent it in on an insurance claim once I received my replacement. They received it already and everything was fine with that one also.
175.00 deductible via Assurant (TMO Jump insurance)
I filed claim in the morning and they processed my claim and shipped same day. Phone was brand new and arrived the following day. I was impressed with the turnaround.