I also have a preview edition.
I moved HA from my server to a HA green to separate reliability (my server is a test bed and uptime isnt great, and home automation warrants better uptime than I was giving it).
The voice services don't work as well on the green directly, but I view it as part of the HA ecosystem and I want it running on the same hardware, but it seems very much like not a great option for that. And even on my own hardware, it still seems like it was a bit slower than I'd want and not always accurate. I definitely need a lot of tweaking (just like OP) to make it worth while.