There has been a lot of discussion in these forums about Instant Book! I personally would never use it, and would 'snooze' my listing if it was imposed on me - ie, still take the guests booked in but not take any more via IB. Many of us have complained to Airbnb about IB being imposed on hosts against their will, and you can too, via the feedback page.
Here is the link: https://www.airbnb.com/help/feedback
IB works well for some hosts but not for others, especially if it is a private bedroom in your own house, or an apartment/house where you want the guests to already have good reviews or chat to them first.