I installed the ARD in the rear of my hardtail yesterday, I'm not convinced it will do much, but it was easy to install and weighs almost nothing.
I think it will provide some time protection but not much sidewall/rollover support, which might make it a little useless since it still doesn't really facilitate lower pressures if that's the case, but we'll see.
At about 1/3 the price and 1/3 the weight and easy install I could see it having its place though. But I kinda think if it's not a pain to install, it ain't doing much.