No problems with mine, but it can get a little hot on the top of it, towards the very back in the middle. Also gets hot on the very back in the middle. It only seems to get hot when I've had it turned on for a long time.
Although I haven't had any problems, I did get these 4 hex nuts from Home Depot to use as extended "feet" for the PS4. They keep the PS4 about 1 1/2 inches to 2 inches above the ground, to hopefully allow for more airflow underneath the system. I used to do the same thing with the 360 and PS3 in the early days. I always like to raise the system up a bit more off the ground. I feel like the normal "feet" don't raise it enough.
The Xbox One might have better feet on it, since it can't be stood up vertically.
I've also heard about people using little usb fans on the back of their PS4. I've considered getting a usb fan that I can plug into the back of the PS4 and add a bit more air flow back there to help it keep cool, but since my PS4 is functioning properly, I haven't actually got any usb fans yet, but I've thought about it.