Formidable is 1) very well thought out to be easy enough to use while providing sufficient breathing space to customise and add deeper coding and 2) its stand-out feature is the quality, care and consideration taken with forum advice. Pretty much every single entry on this forum gives some useful information and is politely given. I have purchased a number of premium plugins and the support varies wildly; this is the best money I've forked out.

I looked at Gravity Forms, Contact Forms 7 and Formidable before settling on Formidable Pro. Aside from having a lot of features I was looking for and being pretty easy to deal with, the 2 things that won Formidable for me in the end was having a free version that I could try and the tremendous support that Steph provided @ strategy11.com forums before I was even a customer.