Long story, get comfy.
I've dealt with BenQ RMA a couple of times here in Finland. First time they shipped me a brand new monitor before I even had to send back the old one, which was pretty nice. However, the new monitor was, surprisingly, defective in exactly the same way as my old monitor had been, and I tested various combinations of cables and GPU's to make sure it was indeed the monitor's fault. I was very surprised... As was BenQ when I told them the new monitor also needed be returned. They wanted to take a look at the old monitor first, to see for themselves what the issue was, so I kept the new one in its packaging while they investigated the old one.
Weeks went by... I heard nothing, then I semi-forgot about it. Another month later, I realized I still had the new monitor packed away, and emailed BenQ about the lack of communication on their part. I think they thought the new monitor was working fine, even though I had told them it was defective and even had sent a picture of the messed up screen. Regardless, they were quick to pick up the RMA case again and I sent the monitor back and got a replacement within a few days. This time though, the replacement was just a refurb, and the package looked like it had been used and reused a lot. I had packed my DVI cable into the box where I sent the defective monitor back, but since they didn't send the cable back to me along with the refurb, I had to specifically ask them to. On the plus side, FedEx delivered it the very next day.
Well, that's not all. There were a dozen horizontal lines running along the refurb's panel. They were one pixel thick, and the difference in contrast to properly working pixels was small enough that it took me a few days of use to even pay attention to them. But once I'd noticed them, it was impossible not to be distracted by them, and I requested, yet again, a new unit. A week ago, I sent back the refurb, and I haven't heard anything from them yet... Still waiting for a working unit after almost 3 months since opening the RMA.
TL;DR - Service is free and generally fast, but not the best quality. And don't count on receiving a unit that actually works as intended.