I just tried "http://www.youtube.com/watch?v=2ZCUtnuAXg8" and it works fine for me...I'm not sure if anything other than "v" in the query string would cause the app to fail, but like the app front end says:
Enter a valid YouTube.com video URL:
If other types of YouTube URLs dont work for you, then you'll need to write your own code to handle those URLs, or write some code to validate URLs so that they conform to the example URL format. (I didn't really program any validation because I'm just using this app recreationally, for my own personal use.)
Hope that helps....Good luck!