I have been searching for several years for a plugin that enabled WordPress to be used to create, store and display customer data. There were a few solutions that did part of the job, but none that got it done completely.
Then I find Formidable Forms and I hit the jackpot!
This plugin not only provides simple forms (as do many other plugins), but it adds the ability to store the data they collect; edit it; import/export it; display it in WP posts/pages/widgets; show statistics for it and much more.
So at a stroke, by using FF you can use it to turn WP into a sophisticated data entry and reporting system, without being a database expert.
I've purchased FF Pro and I've been very impressed with its functionality, documentation and usability.
I can't recommend this plugin enough - congratulations to the developers (Stephanie & Steve) on a magnificent achievement.