I like how easy it was for me as an amateur designer/developer to create my own custom voice menus using one of their pre-built templates or by creating them from scratch with no coding required! The only thing that could be improved upon would have been some additional tutorials provided in order to get people started more quickly.
It's not just about designing your menu - but also learning what you need to do once everything has launched so they can't change anything without calling someone who knows those things too (which isn't always possible). Having created our initial prototypes we were able to present them at trade shows where clients really liked seeing something tangible which showed exactly what their customers would hear once they'd actually used the product.