The learning curve is a steep but short. Once you learn about 4 basic commands, you can start working and learn more as needed.
However, the old news is that Ubuntu has once again tried to make another powerful tool of the Linux world more accessible and user-friendly for the masses. Ubuntu by default installs the package 'screen-profiles' which adds a couple of nice text interfaces and predefined settings to help new users learn the tool.
That is all well and good and I applaud this move. However, if you are an old or advanced Linux user, Ubuntu's move might interfere with some of your daily work. The screen-profile's try not to interfere with a ~/.screenrc file, but they still can slightly.
Uninstalling the package will solve most issues, but there is one very VERY important feature that has been changed as a problem prevention step for newbie users. In some shells and within Screen itself the command CTRL-s if used inappropriately with other key combinations can cause your visible text area to halt until CTRL-Q is pressed.
Now, I use CTRL-s for searching my Bash command history and for saving within my Vim session. So I safely use CTRL-s and I want it around and not interfered with their problem prevention. To get around Ubuntu's new default configurations, simply add this line to your ~/.bashrc file, or type it on the command line whenever you open a new screen window.