The biggest blocker has been the issues with the Android client. I'm either hitting https://github.com/tailscale/tailscale/issues/915 or https://github.com/tailscale/tailscale/issues/4611, but neither issue appears to have a fix coming soon. Whenever I am on my carrier's network, my phone's internet stops until I disable Tailscale - that's just a show stopper from using TailScale.
So instead of developing this SSH feature, I would have preferred to seen them work on their bug backlog.
In the meantime, I'm experimenting with ZeroTier. While it doesn't have the ease and cool magicDNS+LetsEncrypt feature, I think I'll survive with something more reliable.