Well, after more than a decade of using Insteon I've dabbled with z-wave, and it reminds me of my early days with X-frikken-10! Do I really want to put up with a HA system full of weird latencies, unknown states, and "disappeared" devices -- again? Sure, Insteon is bad in some ways, but from my perspective z-wave (as it currently stands) is worse.
It sounds like the consensus here is that Insteon will dry up and blow away. OK, I could live with that, but if my choice today was between z-wave or no HA at all, I'd skip the headaches and ditch HA completely.