I had a transponder die - the light was on and a handheld reader said it was working, but it wouldn't hit the track sensors at two different tracks. AMB said this wasn't supposed to happen. I sent it to AMB for evaluation and after numerous calls on the status, all I could get was "It's being looked at by the folks in the Netherlands." Almost three years later and I'm still waiting.
I bought a new unit last year. Shortly after, I found out about the 50% off program for old transponders. So I called them up and asked if I could get the discount for my purchase, since I had already "turned in" a defective unit. They said they would be happy to sell me a another new unit at half off. When I pointed out that I had already sent them a trade-in, they said they weren't supposed to give the discount after the fact, but they'd look into it and get back to me. Needless to say, I'm still waiting for a response.
This is the sort of service you'd expect when the people you are dealing with have an effective monopoly on the product they are selling.