How to find out the right things with an questionnaire?

I'm currently running an experiment where the Loom (Woven Stories) is used for on-line debates. The aim of this experiment is to clarify following issues:
1. How well does the Loom fit for on-line debates and discussion in general? (Added value?)
2. Is Loom easy to use and learn

In order to get the data for my research I'm logging all the actions and the data the users do in the system that are related to documents, sections, edges and chat. However, this data is not really sufficient in order for me to answer the two questions above. Due to this a questionnaire is needed.

In this presentation I will introduce the ongoing research on such detail that participants can understand it. I also will present the draft of the first questionnaire and try to reason why it is like it is. Based on my presentation I would like the participants to give me hints and suggestions how the questionnaire should be composed in such way that it would help me to answer my questions. Also I would like to have comments about me research in general.

Draft of the questionnaire might or might not be sent to participants before the actual conference.