BaseApp is no longer maintained. There is a very good alternative called bort.
For the impatient: http://github.com/ariejan/baseapp
Got issues? Feature requests or patches? http://baseapp.lighthouseapp.com/
Every Rails developer has at least once developed an application that needed user authentication and some basic UI features like tabs and a sidebar. Ask yourself now: “how often have you installed and extended the restful_authentication plugin?“.
Yes, I have done it quite a few times and everytime I find myself writing the same code over and over again.