I have used StaffPad for a couple of years. An example of its output are the arrangements that I recently made available at IMSLP.
Piano:
https://imslp.org/wiki/Images_pour_orchestre_(Debussy,_Claude)
Strings (cello quartet):
https://imslp.org/wiki/3_Preludes_(Gershwin,_George)
It is serviceable, but there are a number of things that cannot be accomplished as it does not offer particularly flexible layout and spacing.
In terms of its automatic transcription, I have not seen anything convincing beyond simple, fairly predictable 3/4 or 4/4 figures at a slow pace.
Even the demonstration videos by one of the developers doesn't show anything complicated or in a fast tempo.
It's pretty flexible in terms of stylus input, but you have to learn to do it exactly as shown (the program does not accommodate, or "learn" anything from, the user), and certain workarounds are necessary otherwise the program often doesn't recognize the input. If you get used to using it, it's pretty quick, and it's the closest thing to pen and paper. The selection/moving tools are good.
The tool is perfectly adequate for producing parts for recordings or concerts, but you would need to export the Music XML data to a professional music engraving tool if you wanted to publish it.
My 2¢