The purpose of a closed cell foam pad in your camping kit, is to insulate. It also serves as a little bit of padding, but your body weight (or at least mine) will compress it enough that it only has a minimal padding effect. But all those little bubbles in the foam hold air inside them, and this prevents the ground below your tent, or the wind beneath your hammock, from sucking the heat out of you. Open Cell Foam would do this as well, but there are a number of reasons NOT to use open cell foam for this. First of all, it is basically a sponge. It'll suck up water and hold onto it. Not something you want to lay on, and not good for the conditions you're likely to be in. Second of all, having dealt with open cell foam in various applications (halloween masks, these old rolls of it we had for sleeping on, various cushions and upholstery) it gets old, and it gets dry and it breaks down. If you get even a speck of the dust that they make when they get old into your eye, it is an awful thing. NOT something I want to sleep on.
There are more advanced pads that fold up squarely, or have dimples/eggcrating, but in my experience none of that justifies the added cost of them. They all pack up to roughly the same size, they all weigh about the same, the primary differentiation is on cost.
Would I recommend it? Yup! It's a good deal on a simple, humble piece of equipment. Anything more expensive and all you're buying is dubious bragging rights. Final note, if you have to travel by amtrak with this, attach it to your backpack vertically, it will just BARELY fit horizontally through the staircase. and be prepared to fast-detatch it to fit your bag above in the luggage rack.
Potato-quality shots of mine in my hammock at flint ridge:
Gear Tied, Vertically to my pack (high cliff state park):