I like that it is so easy to use, with almost no learning curve at all! The fact you have such an extensive library of workflows (and they are free!) makes this tool very powerful for automating repetitive or complex business processes in our B2B eCommerce platform - we've saved hours upon HOURS per week by using NN's workflow automation features rather than having staff manually do them themselves each time something needs doing.
Nothing really comes up as being dislikeable about how things currently run; however there isn't anything specific either which would make me say 'this must change'. If your looking into any type/kinds of automated process then look towards these guys!! We're saving TONS OF TIME every day because their service has made us not just efficient but also saves money too through reducing manual labour costs within my team alone.