(New) Poker II user here. After seeing it suggested, I moved the FN key to the CapsLock button and I think it's great! I actually prefer the arrow cluster on the WASD keys, because now I don't have to move my hands as much. You should note however, that selecting text (Shift + arrow key) or any other command that requires an arrow key + another key is not going to be very convenient. I don't program or use any arrow-dependent activity, but I do use them a lot while typing/browsing. So to answer your original question, arrow keys are pretty easy to get used to and personally, I find their new position more ergonomic.
I just realized how often I use the F keys. I use alt+F4, F5 to refresh web browser, I use F1 and F2 for voting options in CS:GO, I use F3 to buy default buy-round loadout in CS:GO, I use F4 to buy previous items in CS:GO, and I use F5/F12 to take screenshots in steam. Based off of those facts, I at least need a 75% board, and I would want NKRO, and I am not finding any 75% NKRO boards out there.
There are two FN keys on the Poker II (one in each side), so hitting FN + a number key isn't any more difficult than usual. Again however, any command that requires an F key + another key is not going to be convenient.
