So, it turns out that the rMBP's highest native resolution is scaled-up 1900 (or thereabouts), which is lower than what all the ads say (which say 2800). Right? I know the pixel density is the key factor, but I'm referring to screen real estate. My desktop has 2500 resolution and a Photoshop A4 canvas (300DPI) fits onto the screen without any scrolling. My understanding is that the highest scaled resolution on the rMBP is 1900-odd, which means that an A4 Photoshop canvas might not fit on without the need to scroll. This is where SwitchResX comes in, I suppose? I hear that it can change the resolution to 2800. Is there a performance drop at this resolution?