i guess it's mostly a matter of getting used to it..
it took me a few weeks to get used to the smaller backspace and smaller (right) shift keys, but once i had, it was absolutely not a problem anymore (that they were smaller).
getting used to left alt, left fn and left alt also took me a few weeks.
but after 17+ years of using a standard layout (fullsized keyboards), i think a few weeks to get used to a new layout isn't much time at all. (besides: it was worth it!)
what i liked immidiately was how home, end, pgup and pgdn are located on the arrow keys, because it allows you to easily use the right Fn key with your index finger and then use your middle/ring/little finger to press one of the arrow keys.
because of the small size of the keyboard, your right hand will always be close to these keys. i'm positive i'm using less time to press home/end/pgup/pgdn than i did when using a fullsized keyboard.
using the arrow keys might feel funny (in the beginning) when your left hand is also using the keyboard, simply because they're located more to the left. so let's say you'd play a side-scrolling videogame with wasd and the arrow keys, then you'd notice your hands are closer together than you're used to.
but also this is just a matter of getting used to, from my experience.
i suppose it could matter what you plan on doing with the board, though.
maybe the layout would be less effective for a coder. i wouldn't know, though (i know nothing about coding).
TLDR: i bought the pure pro because of the dedicated arrow keys and its small size, and i am not quite disappointed :j the layout is absolutely no issue for me and i definitely like the fact that it has two Fn keys.
(if you're a coder, then i think you might want to wait for at least one other coder to share his opinion.)
