WiFi congestion is a big issue in a large apartment building. However, I see no label on my box that says I must live 50 miles from anyone else for this product to work properly. I keep my apartment fairly cool also (about 45F) as I love the winter and have ridiculous A/C for the summer. I have taken the temp gun to my RT-AC66U with that under more load than the DIR-857 could ever take an it doesn't even touch 40C, let alone 50C. Before I bought the Asus, the D-Link was seated in the same place. Everything in here is plugged in to APC Surge Arrest 11's that are rated for commercial use. Again, no complaints with the Asus RT-AC66U. My DIR-855 holds up better under full load than the DIR-857 does with light use.
Before I took this thing up to my cottage which is in a fairly rural area, I had talked to D-Link about it, posted about it, and tried a few different internal beta firmwares that were sent directly to me from Pardeep Vahra with no real improvements. I gave up on it for home use and took it up to my cottage where I barely use it for anything other than web browsing. My cottage and being a few miles away from anything, this router still tops 40C easily and hits 54C under heavy loads. Even using the PowerLink Boost N for WiFi on it with the WiFi for the DIR-857 turned off, there were times it would just stop sending traffic. I was never offered an RMA and as stated, I moved on with a fantastic product. Considering I have owned D-Link after D-Link all the way back to the late 90's. I have come to the conclusion that their products just aren't up to the quality they once were. I do hope everyone else has a much better experience with the current product line.
Furry and Patrick, you both do great stuff here and D-Link is definitely lucky to have two excellent posters that are as thorough and knowledgeable as you both are.