WordPress is the most popular leader in the open source web industry and started as a blog platform it developed itself as a grown up and a mature CMS system. Currently more than 4M WP-based websites are out there (I definitely believe they are at least twice as much - the Counter states there are 12M downloads in WordPress 3.1 only, and there are 20M websites on WordPress.com . Nice, huh?
WordPress supports most of the popular modules like posts, pages, users, links and categories, media (for uploads), lots of settings etc. There are some other powerful free mods for caching or SEO as well as 15K public plugins in the repository. However there are few weak points for WordPress sites that take time to create - such as creating forms.
Forms in a website could vary - Contact Form, Registration Form, Enquiries. The basic idea of a form is - fill in content, send to the administrator (or persist in a database). No such default behavior in WordPress and basic plugin functionality is available only.
Gravity Forms is the leader of the "forming industry" out there. When you need a professional help to build your request on the form, Gravity Forms is the answer. I had to do a kick start with the plugin to define a real estates website with step by step confirmation process based on a form. The form itself had 2 branches - so I had to use some conditional logic and define many subforms that were going to persist the data from every step and each step to be defined based on the choice of the previous step. It sounds a bit blurry and yes, it actually is. A true story looking like a real world solution.
What actually made Gravity Forms the answer was the fact that it had in built step-by-step wizard with conditions, with ability to add different field types such as inputs, dropdowns, HTML blocks, file uploaders, email fields (with validations) and more. By default Recaptcha is available and you could integrate only in a step Really Simple Captcha with the Gravity Forms plugin.
You can use widget or shortcode to activate Gravity Forms - hiding the description, the title and the steps counter is an option to be done. What helps me big time in GF were the HTML blocks - could be defined everywhere and there you can actually do your magic when the lack of layout manager ties your hands.
Records from the forms are mailed to you and persisted in the database. The data could be exported and imported in some sample CSV format as well. There is a complete documentation available for the subscribers including 1-year support too - and I really enjoy the support on Twitter which used to be amazing.
As a supporter of the plugin I joined the affiliate program and started spreading that piece of software. I do enjoy open source big time, but here you pay about monthly updates and 1 year support of the highest quality which shines compared to most of the free plugins on the market. I consider buying the developer license of Gravity Forms for my next forms-based website.