It is large enough and dune-y enough that you cannot see the entire thing unless you are in an aircraft. It is eminently photogenic as well.
It is a nice day trip from the Springs, and if you rent a sand board in Alamosa or some such place, you can spend several hours sliding down and slogging back up. Personally, the up-and-down wears me out after only a couple of hours, but if you have kids, you can dig yourself a seat and watch them knock themselves out.
Unlike the sand dune areas around Yuma, I have never seen dune buggies or motorcycles on it, so you don't have to keep your head on a swivel at all times to avoid being run down.
Here is a thread with recommendations about the area:
https://www.flyertalk.com/forum/west...-dunes-np.html