Is there Merit in Reservations?

Is there a merit in reservation? As many comments on the previous posts allege, the benefits of reservation are supposed to have been cornered by the "creamy layer" or by those who don't actually fit into the criteria of being "backward".

On the other hand, a nation cannot develop on a sustainable basis, unless certain radical reforms are implemented to tackle the issues of social disparity and unequal opportunities. The arguments on both sides (pro- and anti-reservation), however, are largely based on ideological or anecdotal evidence.
My own mental analogy has been like this: if you spray fertilizer in a field - real life not being 100% perfect - it will not only help some plants to grow and bloom, but will also kill some plants due to overdose, and it will also often facilitate the growth of the weeds for whom it was not meant. But the effectiveness of the fertilizer is measured in propotion to the aggregate productivity of the field. And so, in this current debate about the reservation, one question begs an answer:

Is there any empirical evidence to show that quota has really helped?

And if they have not done in last 60 years, how can one be sure that they will do so now?

The Southern Four states (Kerala, Tamil Nadu, Karnataka, and Andhra) have had 50% or more reservation in higher and profession education for many decades - even before the Mandal Commission in late 70s.
If the distributive justice that the reservations aimed at had really worked, then there should be some positive differences between southern and the northern states.

In one of the earlier postings (pt.10), I had quoted how in Tamil Nadu (which has had 69% reservation since 1960s), in 2004, students belonging to the Backward Class (BC) or Most Backward Classes (MBC) quailified for 952 of the total 1,224 seats in 12 government medical colleges in the State (77.9 per cent), and the first first 14 ranks in the medical admissions went to BC/MBC students.
But, as one would point out, getting into a medical college through reservation, is different than becoming a good doctor (or as someone cruelly commented: "would you leave your life in the hands of a SC/ST/OBC doctor who got into the profession through reservation?")
Following this line of enquiry, I stumbled upon this report on The Merits of Reservations. It is based on the data from the Planning Commission's National Human Development Report 2001:
As the table below shows, apparently, at an aggregate societal level, reservations in healthcare education have had a positive impact on the society: