My main objection would be that the weight penalty, higher build cost, and increased wear & tear potential far outweighs any rough terrain performance gain. The travel on the Activator suspension is very short which means it's usefulness is really limited to improving rider comfort a bit and taking some of the sting out of bumps.
The bikes are certainly robust, but then so is something like a Raleigh Ascender rigid that is lighter than either version of the Activator, and was considerably cheaper to buy. A hardtail Activator would make an interesting back to back ride against a conventional rigid MTB, so I wouldn't turn down a dirt cheap one just for the opportunity to try it, but I wouldn't go out of my way to look for one.
Compared to today's suspension BSO monstrosities the Activator doesn't look that bad, but I can't help thinking of them as a solution t a largely imagiary problem.