I can say I am a poweruser of this extension.
I use it for contact forms, PDF quotation generation, automatic user content upload, invoice calculation, questionnaires, online surveys etc etc
The basic setup is very easy, and once you dig deeper into the extension you can design some complex stuff.
I am using it for a few years now and I believe I have only scratched the surface of what is possible.
Basically this extension gives you the possibility to design very nice forms and use the user input for whatever you want. Send custom emails or PDF documents, it is all possible.
Support is excellent. You can get a lot of information in the FAQ's and forum and for paid subscriptions you can post in a special suport forum.
Sometimes you have to wait a bit to get a response but if the problem is to difficult to resolve immediately, you can send the developer a PM or email to get some specific support on the matter.
The only downside is that there are a LOT of undocumented features in the extension. Getting advanced functionality will take a lot of testing.