NIOS is basically for students who are poor in academics. Take for example a student of SSC/CBSE or any other state board, if their results are poor and when parents are sure they wont clear the 10th/12th board they opt for NIOS.
In NIOS for clearing 10th, you can take some 7 subjects and in that you need to clear minimum 5 or 6 (Not sure). There are projects which adds up in your final marks, which makes your passing very easy. The course-ware is comparatively easy if you see the syllabus.
Mostly you can do it on your own. I mean no need to go to school. Just fill up the form and get the books and all. They will mail you for project dates and final exam dates.
How good it is with other board?
-This is tricky. NIOS has a good reputation but still many colleges don't prefer NIOS pass-out students.