Great promise, but with the possibility to create a an architecture of chaos if not governed right.
What do you like best?
Speed of development, good overview of applications, good automated suggestions to improve code. One thing that's absolutely great about outsystems is that everything seems to be connected and actually works... example: changing a column name in a table will be reflected immediately across all forms, queries and logic where you've used that table. I've seen many flow editors, and outsystems is one of the best.
What do you dislike?
The fact that this speed comes with a price of bad architecture in the absence of a Domain Architect. It's too easy to create dependencies across modules, without a proper API Manager interface. Point to point connections can be created almost unknowingly.
Recommendations to others considering the product:
Have an architect present at all times. It's too easy for developers to make a mess that is disconnected from the actual Business Domains. It's too easy to create point to point connections, even if outsystems does provide all the right tools to create a good architecture.
What problems are you solving with the product? What benefits have you realized?
Invoicing, Payments, Mobile apps, integration API's. All with great speed. Last thing we've implemented was a paypage, that calls an API from a credit/paypage company. It took 2 days to implement, including UI. One other thing that's important is that litterally any developer (front end, back end, database etc etc) is able to use outsystems in no time.