PDFfiller works well and is intuitively easy to follow. I used it for my company's W-2 and 1099's. The forms could be easily found, filled and printed without any problems.

Performance is slow and choppy at times. There is no OBVIOUS way to turn off the popups every single time I go to fill out a form. Transitioning from one form to another is extremely disjointed. There is no clear way to fill out one form and simply move on to the next in a series. If there is a clean workflow in there somewhere, it's not obvious, at least, not for my use case, which is to fill out a form for each of my employees from a remote location, download all and print all for distribution. Seems like every time I finish something, it takes a while to save, and a while to get to the page letting me choose what to do next, which is always to display the file list again, and a while to load the file list. . .rather than simply keeping the filelist persistent and hidden, as would seem same here. Also, this form, won't let me enter more than a character or 2 before kicking me out. I am writing this feedback in a notepad and then copying it in all at once. Awesome.

Filling in the pdf was great, however when I saved the file using "Save As" the text was not spaced out in the boxes but overwritten making it difficult to read.

I am a learner, and have taken so much time to get the taxes into IRD so no time to spare. Used it to sign another form the other day, and I am getting to know the process, slowly.