My experience with Appian.

Lack of version control and being different for all modules.

Expression Language is a Lisp dialect - that forces functional programming. JavaScript or VB would be easier.

Several users working on the same module might create problems. No individual work space.

API is not well documented with comprehensive examples.

Functions do not work well with large numbers when they should.

Training exercises are full of mistakes - that turns training into the worst experience. Training MUST be improved to provide quality good examples, and not guesses what should be there but was missed. How can one learn - if training examples are a trash, while the exams ask questions on topics not covered????

Too much documentation. Must be much, much more concise. Who can read and memorize so many pages of Appian "Britannica"???

Some errors are captured during editing, while others are not, or show up in a different window????

GUI widgets lack numerous hooks to make design more creative. Need access to all widget features. Otherwise developers are limited to "limited" widget behavior.

Response in a cloud could be too slow, following data entry. For example, one enters a name and validation takes up to a dozen of seconds.

Development environment is not coherent between different objects, some can only be edited using old GUI. A lot remains to be done to make development environment simple , intuitive and coherent.