Updating the gem broke Jekyll, had to revert back to 1.4.1 to get it working again. On 1.5.1 it would no longer detect changed files.
This is on Ubuntu 12.04 using Ruby 1.9.3-p385
Fixes for directory_watcher 1.5.x integration. Closes #916.
On ubuntu 13.04, directory_watcher doesn't work again. Have to roll back to 1.4.1. Here is the stackoverflow post
I also get the same on OS X 10.8.2, using Ruby 1.9.3p125.