Jon,
Installed the pre-release version and I have 4 Dots and an original Echo and it works perfectly. The activity is routed via the Echo which was my first device. Not exhaustive testing but the responsiveness seems much better and thus far I have had it respond first time, rather than having to repeat commands to "wake" them up.
Thanks for your work and I will keep you posted if I spot anything. I have a spot arriving tomorrow so will have a play with that.
Neil