Great Box, UI needs work.
The latency on this thing is negligible. Even listening to the final live mix with a microphone plugged in to the 6i6, routed through the computer and Ableton for reverb and effects, then back out through the 6i6 there was no discernible delay.
Playing live with it, though, I'm not a fan of the low-contrast gray-on-black 'material design' on the Focusrite Control software. The button and slider icons are very small on a 15" screen, and the chosen colors don't help visibility. Forget checking the positions at a glance. Though the bright green level meters are plenty visible, they further obscure the slider positions right next to them.
Another small thing is that the inputs you choose are global - they all stay visible no matter which output you have selected, though muting and volume are controlled separately for each output. This arrangement might make it easier to change inputs on the fly, but it makes the feel kludgy, as the display doesn't represent your chosen routings. Larger, more contrasty controls would help this, as would dimming muted channels, but I still think allowing unused inputs to be hidden per output would be more direct and intuitive.
Still, these are very small issues in a great overall product. Most people running live will set the routings once and use a mixer or DAW to change levels, if they don't have a sound person doing it. If you're using it in a studio, these small UI issues become less than noticeable. Excellent low latency makes the direct monitoring feature, though nice to have, hardly worth mentioning, and the build quality is superb.