I don't have the stall matresses, but I've boarded at several places that had them. The matresses are fine and dandy, but I find that the barns that had them ended up skimping seriously on the bedding and the horses were standing around in their own pee. I don't think they are a substitute for an adequate amount of bedding. In my own barn I use traditional stall mats and pelleted bedding (Magnum brand). I find that the pellets fluff up very nicely if you add some water and are less dusty and more absorbent than regular shavings. In my opinion "soft stalls" or stall matresses are not worth the $$$.
I am in need of new mats and was also considering the stall mattresses, there is also a foam mattress option as well. I do think the horses would like these better to lay down, but was wondering how they were to stand on. I know for myself if I'm on concrete, I like to have some cushion so my feet and legs don't get as fatigued, I think as long as they were not too cushy it would ok. Definitely curious to hear what others have to say. We'd be putting these in on a crushed stone base vs. the concrete most manufacture recommend, has anyone noticed a difference?
I personally wouldn't, and neither would the horsemen/women I know of. Horses naturally lay down on the ground. They don't need bedding for softness, although their owners might need them to have it. I think that's transferring human values onto horses, once again. I like stall mats to reduce shock, but not to add softness- I am certain that would contribute to soft tissue strains. Mats with enough bedding to absorb liquids are fine.
I'm with the plain rubber mat contingent, and not just because they're cheaper. Clearly, puffy pillows are not what horses (or anyone) evolved to stand on. I've tried it, and it's annoying. Constant rebalancing is beneficial for a minute at a time if you're rehabbing an ankle injury, but standing on it all night? A pal of mine boards her zillion-dollar WP horse on a mattress. It's always got some kind of ligament issue or other. Coincidence? You decide.
In my vast experience, I've found that what horses really like to lie around on is dirt.
Dreadful Acres: the chronicle of my extraordinary unsuitability to country life