To answer your question about what Qlikview is, I would say its more of an analytical application that allows the user to consume the data they are interested in fairly easy. You could build reports with it.
As far as requirements gathering goes, I would say that gathering business requirements should be technically agnostic. The main goal of the requirements gathering process would be to understand the business problem they are trying to solve with technology. Once those parameters are determined, how the solution will be addressed should be the next goal. Understanding the data relationships is key with Qlikview. Coming from a SQL/SSAS background, I struggled at first to understand what Qlikview does with data relationships. Once you understand how Qlikview creates and utilizes data relationships, the application becomes more straight forward.
The overall development time is alot shorter as the application is very developer friendly. Having short JAD sessions with the users helps solidify the requirements and shows the users the capability of the application. Overall, I have found it to be one the easier BI dev tools on the market.
Hope that helps.