I was initially dubious about using these types of components over a standard (free) form component. But my was I wrong. Installing and using Babel-U-Exams was a simple task, creating multiple categories, exam questions and responses, with randomisation and the option of multiple answers, weighted per question scoring, pausing of exams and automated grading all make this one of the best components I have used. I've not even mentioned the results a user can be shown or the absolutely first class support provided.
I highly recommend this extension.
The only extremely minor item is the ability for a user to complete a personal details form before the exam but this was solved by modifying the standard Joomla login / registration module, and I'm informed this is coming in a future release.
Don't waste time with other components, get this one today!