Atlantic, I HATE playsand as a substrate. I spent 15 years as a veterinary surgical tech and saw over 1300 bearded dragons die as a result of playsand impaction in just 5 years! I don't recall any plated lizards but they are not easy to find around here. Many other reptiles had trouble with playsand as well.
There is a type of impaction called chronic impaction that even most vets don't seem to know about. I was lucky enough to work with a bowel resection specialist and so learned more than I ever wanted to about chronic vs. acute. Everyone knows what an acute impaction is. Sand forms a clump somewhere in the gut which blocks off everything and the animal cannot pass it.
Chronic impaction is much harder to diagnose. It doesn't even show up on xrays but sometimes will on an ultrasound. It happens when sand grains cling to the walls of the intestines. These walls are not smooth like sausage casings, they are full of these little fingerlike projections called villi which absorb nutrients and help the food to move downstream. The sand often gets caught up in these villi and stays there. Over time, it builds up enough to block off the absorption of food and the animal slowly starves to death. For a bearded dragon, the average length of time is 5 years before symptoms of malnutrtition are seen. We didn't keep stats on other types of herps because we just didn't see the caseload that we did for bearded dragons. David, the bowel resection guy, has spent almost all of his career working on chronic impactions, in animals of all types. He's done surgery on elephants, ostriches, horses, parrots, reptiles, all sorts of creatures. He has a twisted sense of humor and says that the playsand industry is putting his kids through college and graduate school.
Sometimes if the sand buildup is severe enough, the underlying tissue cannot get enough blood supply and begins to die. Sepsis sets in and the animal dies of blood poisoning secondary to the sand impaction. This can happen very quickly and usually isn't treatable.
A quick test of chronic impaction risk is very easy. Wet your hand or foot and bury it in the sand you are considering using. If the sand clings and you cannot easily shake it off the same thing will happen in the gut. The finer the grains, the higher the risk.
I bought a 5 week old bearded dragon from a breeder who used to keep their hatchlings on playsand. Matisse was never seen to eat sand but was an average beardie, actively tongue-flicking and so probably picking up a fair bit of sand from time to time. Knowing what I do about chronic impactions, I asked my vet to do an epigastric lavage to flush all the sand out of the digestive tract. Here is the result:
<img src="http://www.thebeardedlady.org/images/sand.jpg">
I actually prefer coconut husk. It's the only substrate I've tested that passes the hydrochloric acid test for digestability. It dissolves completely when placed in a beaker of 5% HCl for 20 minutes . Bone aid is probably the worst thing you could use, it actually forms harder clumps as the calcium carbonate is an antacid so it doesn't allow for natural digestion to occur at all. It's much more likely to form an acute impaction than playsand.