The xip.io DNS servers are proving to be troublesome for both latency and reliability. In researching solutions, I found the nip.io DNS servers to be much more reliable.
This modification to add nip.io support is for version 0.5.0
of Pow.
Go to line 78 of the file ~/Library/Application\ Support/Pow/Current/lib/configuration.js
:
this.allDomains.push(/\d+\.\d+\.\d+\.\d+\.xip\.io$/, /[0-9a-z]{1,7}\.xip\.io$/);