As an example, I recently tried my hand at making a Chrome extension using the Yeoman build tool. It was a simple plugin to allow you, on Reddit IAMA pages, to hide all comments except those from the IAMA subject and their direct questioners, and to also auto-load all comments:
https://github.com/dannguyen/iama-highlights-chrome-extensio...
Figuring out how to use the yeoman build tool took about 30 minutes (it's not quite fully developed)...it took about 30 minutes to browse through the Chrome extension documentation and then think of what I wanted to do. About 10 minutes to write the actual jQuery.
...And then about 3 - 4 hours figuring out why the comment auto-loader wasn't working. I thought I could simply just have my jquery activate the "click" event on all "load more comments" links...but a recent Chrome upgrade clamped down on security, effectively sandboxing all extension code and preventing it from executing existing inline JavaScript.
IMHO, this is a good security measure. But it just goes to show you that when things are made "easier" (the scaffolding of the extension, the jQuery to do DOM/AJAX work), there are still intractable tradeoffs and details that have to be dealt with...in this case, security.