This sounds like a caching issue. In 3.0 widgets.js is loaded from the cache, as long as the project is not redeployed. To avoid that widgets.js is loaded from the cache, just clear the browser cache (ctrl + shift + del). If widgets.js can not be found in the cache, and does not exist on the server, all widgets are loaded separately, so you can debug your widgets just like you used to do in RC1.