What do you like best?
PDFiller is ultra-convenient and super-easy to use. It's in the cloud, so it's easy to access. And it has a vast array of features. Storage is a cinch, whether on your hard drive or in the cloud.
What do you dislike?
I can't think of much that I don't like about the program. There might be a more direct or seamless way to save documents to Google Drive, in terms of getting them straight into a particular folder instead of just onto the Drive, but that's a minor issue.
Recommendations to others considering the product:
Try it. You'll like it.
What problems are you solving with the product? What benefits have you realized?
PDFiller is a lifesaver when I'm editing contracts and related forms. The clarity of the input and the ability to maneuver the text around the document is a huge plus. Line-outs and erasures are a breeze, making for "cleaner," more legible documents.

What do you like best? I love the fact documents may be completed and signed electronically without the need to print, scan, and attach anything. It's so much easier, cleaner, and more secure! What do you dislike? The only issue I have had, which could certainly be user error, is that one of the links to an informational PDF (it's a read-only document) sometimes stops working. I am made aware of this when I send the link to someone new and the person responds to say an error message appears upon clicking. I have no idea why this happens and it's always associated with this particular document. What problems are you solving with the product? What benefits have you realized? Per my comments in response to what I like best, using this tool prevents the need for recipients to print, complete by hand, scan, then attach documents to an email. It's also a more professional-looking and more secure approach to document sharing.