Might just be me, but when you're walking around, firing your weapon and such, and after some time the weapon HUD element (in the top right corner of the screen) vanishes, then if you at some later point decide to hit 'F' to toggle from say semi-automatic to full-automatic, you have to press 'F' twice, because the first press only brings up the weapon HUD element again.

It's not really a severity issue, and I don't know if it even bothers others, but to me it just seems like an unnecessary extra step.