Besides all that, it is very well documented and brings instant results. I just reworked a small internal web project which was put together with some years ago with totally no UI love and therefore had only minimal CSS applied to it. To be honest – not something to be proud of looking at it from a design perspective.
After an evening of removing the old CSS and bringing in Twitter Bootstrap the application is not to be recognized. It looks like a modern web application even with some responsive design elements which makes it good looking and – even better – usable on mobile devices.
So far I am really exited about the results and plan to use it in more projects. With Twitter Bootstrap even engineers have no excuse why a web application should not have at least a minimum of visual appeal.