Aside from the fact that I have to hold down the FN key to use arrows, the other problem is that if you ever decide to use custom keycaps you'll need to rememeber the entire function layer in your head.
No complete custom sets for me I guess, too much to remember. >_>'
Might just replace the windows, function, CTRL, ALT, Shift and Tab keys when I find them individually, and maybe WASD. (Spacebar is already the Ducky Cities...)