Since I last posted on this topic in 2014, I have had 4 different RNG200N HD DVRs; all have had noticeably noisy disk drives. When powered on, the disk drives make a rumbling sound continuously. Because this is in an office, and the box is on the desk about 3' from where I sit, the noise is noticeable.
And, though I do not know if this is a problem with the box or with the host, the user guide of content takes days to fill out after a reboot (though every Comcast tech I have spoken with says that it is unusual), and it never fills out more than a week into the future.
No, I am not on the X1 system because Comcast has not upgraded the box to allow sorting what has been recorded by who recorded it so the wife and I do not have to search through each other's programs. We still have two HD boxes.