Overall I would say Appian is pretty easy to use. The learning curve for building forms and simple processes is short. However, a significant benefit of Appian is its use of business logic. In this case the user will need a deep understanding of logic statements (If, Or, And, etc). Also, to better use the data then a designer should have a good understanding of setting relationships between data points, building DB views and SQL queries. To realize the full power of Appian it does take someone with some development experience a good 6-12 months to be a well-rounded developer/designer. Also, it will help if the person doing the designing has some information architecture, interaction design experience. Knowledge on how organize data, layout forms, establish design patterns, will make the use of the forms easier.