Here's an absolute bare-bones test.

npm install
gulp

Then, make a change and save test.html

You should see:

$ gulp
[13:05:28] Using gulpfile ~/Dropbox/workingCopy/buddyup/debug-npm/gulpfile.js
[13:05:28] Starting 'default'...
[13:05:28] Finished 'default' after 11 ms
changed
{ type: 'added',
  path: '/Users/skoczen/Dropbox/workingCopy/buddyup/debug-npm/test.html' }