Pros:

• You can build a really simple bot quickly
• Deployment to FB Messenger is easy. They do it for you so no need to go create FB dev accounts, approvals etc.
• Outbound webhook support is ok

Cons:

• You cannot build anything beyond simple, linear bots without tearing your hair out.
• It’s not very intuitive although they have some examples so you can play with those and figure out how to create your own bot.
• Support for branching, variable operations & non-linear conversations is poor or absent.
• Poor documentation.