New Delhi, Sept. 17 -- The National Stock Exchange of India Ltd.'s much-awaited IPO opens today, marking the culmination of a decade-long wait for India's largest stock exchange to list on Dalal Street. The journey hasn't been without controversy, until the last day.

The Rs.22,569 crore NSE IPO is an intriguing proposition. At Rs.1,700-1,785, NSE shares are being offered at roughly 30% discount to rival BSE Ltd. on price-to-earnings, despite being nearly three times its size. The discount reflects a complicated reality: NSE's dominant derivatives business is recovering, yet its growth has slowed sharply.

The issue, a pure offer for sale, was initially expected to raise ~ Rs.30,000 crore by offloading 6% stake but shrunk in size as insti...