Compared with Qt and Tk for Python, where you have to manually code layouts (unless you use some layout generation tools, but they're all pretty iffy), how easy is it to design and code a form/screen/input/etc in Kivy?
If you want to use somethimg else than the default theme however, you might need to do some extra work. As someone else commented, there is a material design theme, haven't used that myself though.