I think having work experience befor joining MBA is really important.....
There are a number of advantages.....
1. MBA curriculum is designed in such a way that it can sharpen the existing skills of the student rather than teach them all the aspects of management ( Which is not possible in two years ). That is the reason why we find most of Bschools around the world considering work exp as a important criteria before selection.
2. If a candidate has work experience before joining MBA he or she will know the reason as to why they are doin the perticular course.... Which will keep them more serious....