Pros
Been working at Nasdaq for 6 years. The experience varies a lot across offices, but employees in general are convivial, like working together and have a positive outlook on life. Executive Management used to be apparently indifferent to the needs of employees, but the level of respect and helpfulness has steadily grown. I feel proud to work for Nasdaq. The company uses macs and PCs, and use both iphones and adroids for mobile. It doesn't ever feel like we're working in the stone age.
Cons
The vast majority of business lines require responsible stewards, not inventors or disruptors. However there are pockets of innovation here and there that a lucky few get to enjoy. That innovation, unfortunately, is often stifled by red tape and endless appraisals of "profitability", even for nascent products that have not come to market. It is the downside of a very conservative company, although this also means that the stock price does pretty well.