Knowing how people think or feel about a certain subject can be very helpful in building trust, creating a team and to reveal impediments. Of course it can be very difficult to get team members to express their real opinions, especially when a team has just started. I think with patience and the right approach trust can (and will) be built and it will be easier to get real issues out in the open. The following practice can help you start this and make explicit what individual opinions in a team are.
I have used the following retrospective practice for several years now: