Despite the naming issues -- my flat pile carpet does not actually have a lip -- but the mat does and it is vinyl. And the little prongy things go DOWN into the carpet. And it works great. Good value and in all seriousness it does not curl as do some. So good on you Staples.
The mat is fairly thin and it will 'dip' from my weight (I'm not over-weight) & chair. It can make rolling the chair on the map a bit of an effort. I don't have plush carpet but the mat still moves a little - not as much as my previous one.
The size and grips on the bottom are working great. It is already indented where the wheels of the chair are. Not sure if that is normal for chair mats.