I think I agree on the cooldowns. Often times I wanted to step away and let the pixels accumulate, but it's hard to resist when you realize you'd be missing out on double or triple the amount of pixels you could be placing. If the goal was to reward the player for actively placing pixels, all I can say is it didn't feel very rewarding.

I kinda disagree about the integer scaling. 1x to 2x zoom is a very big shift without any in-between. It would also feel strange on pinch-to-zoom on mobile without in-between. I think instead it could snap to an integer scaling, or have a zoom slider that works to integer scaling. Overall though I agree, having a way to snap into integer scaling makes the pixel art look better