What would you improve about our product?
This can be a somewhat challenging question to answer but really what the interviewer wants to see is that you have researched their company and its products. You will want to talk knowledgeably about what their company does and make a thoughtful suggestion or two about how they might improve one of their products. Make sure to lead off with some of the things that you like about their product so your response is more positive than negative.
"I hold the SEC filings service you provide your customers in high regard because it appears to be very useful, saving companies money when it comes to analyst salaries and assisting them in making smart investment decisions faster. I would love to lead the team that develops and launches other similar services for your clients. Having said that, if I had to improve upon your service, I would look to automate it even more as right now you rely on a lot of data analysts to parse data manually for you."