I downloaded the Polymer Starter Kit and it seems to all works fine. If I run 'gulp serve', I can make changes to index.html and the browsers all reload and display the changes.
However, if I create a simple html file, gulp serve is not forcing a reload when it changes. This is the simple html file:
<html lang="en">
<head>
</head>
<body>
hi
</body>
</html>
Note when I 'view source' on the served page the gulp injection script is not there. It does not seem to be injecting the script it uses to listen for refresh requests from the server.