What do you like best?
As a beginner, I was surprised not only with the fact that PDFfiller was so much easier to learn and use than the Adobe Suite but also at the range of capabilities on offer! From my first use of this online program I found new pleasure in dealing with .pdf files. I now use the program Every Single Day to create, manipulate or convert files that used to sit waiting, sometimes for days at a time, to be done by the one or two people with access to more expensive and less user friendly programs. Now I have a new "can-do" attitude to the workings of .pdf files. I can't recommend this online tool enough and it's so affordable, you can buy a license to use at home. Great product, lots of advantages. You will not look back, you will not regret this purchase.
What do you dislike?
The user Interface could do with being a little less busy. A streamlined interface and a compact "how to..." would take a 9/10 to a 10. It just needs some tweaking and it's perfect!
Recommendations to others considering the product:
In my opinion it is definitely worth spending the small amount to upgrade to the paid version!
What problems are you solving with the product? What benefits have you realized?
Administration issues generally...adding text, file conversion and commenting on documents...are all problems that I had to either pay to have done elsewhere or ask for an expensive subscription that was never in my budget and wouldn't be approved if I had asked.

What do you like best? Ease of use and broadness of applicability. What do you dislike? Its ease of use and broad applicability trumps any minor issues. I am not aware of any significant issues encountered. I evidently need to keep typing, because I'm not able to finish this task otherwise. What problems are you solving with the product? What benefits have you realized? Being able to fill in PDF's without using more expensive solutions. Also used to authenticate signatures in various ventures. Comes in extremely handy actually.