I believe that Pixel Perfect is the wrong way to go on anything. We have a lot of different of devices from cellphones, tablets, laptops, televitions, etc and each has a different pixel resolution. So in my way of thinking is what would you like a one or two resolutions perfect pixels that look very clean and neat but fails on every other resolution or do you want a design and functional web, app, webapp that runs perfectly on every screen size. Of course all your fonts-sizes, colors, images-sizes, icons-sizes, etc should be the same size but a design should not be perfect pixel. Also as a Front-End Developer, you waste a lot of time making sure that every part of the design is pixel perfect moving something one or two pixels, measuring the psd for every single part and pixels and realising that the design wasn't even pixel perfect and have wrong sizes on every part is a total waste of time. I did a single view in about two and a half day pixel perfectioning it, when I could've done the same stuff with scalable and more responsive perfectioning it in less than a half of the time and the end product is way more expensive and way less adaptable.