It is a very cool piece of tech to be sure, but as a composer who has used notation programs almost daily for over a decade, this really doesn't solve any new problems, and it isn't anywhere near powerful enough for professionals (yet), so most will be importing files from StaffPad into Finale/Sibelius/etc.
With a MIDI keyboard and some keyboard shortcuts I can enter music extremely quickly. To write a string of 8 16th notes, for example, I can press 1 button to select the note length, then press the 8 notes on the keyboard to write the notes (this is with any modern notation program). With this app, I have to draw each individual notehead, beam across the top, and then an additional beam for the 16th notes, then I have to hope I got everything in the right place so that it correctly recognizes my intentions. On that last point, anything beyond very simple scores would probably end up being a nightmare in terms of productivity. A video from last April shows a person making a very common action - beaming more than 2 eighth notes together in a 4/4 measure, but the program thinks he wants triplets, so he has to go back and erase the marking. I can only imagine how many of these "hitches" would pop up in a more complex score.
The price is fairly low, and they seem to promising more features and refinement, so it will be interesting to see where it goes. But the input method, while neat to look at, is fundamentally a regression for professionals. A Vim-style system that allows for extremely rapid entry of music would be an interesting and useful approach, but something that might not have a wide appeal. This app will be useful for those that want to jot down ideas while not at their desktop, and many people will buy it for the novelty, but I would imagine most professionals will wait.
