It runs inside Photoshop (there is no upload stage nor do you have to open up separate software) and it generates HTML and CSS that looks like a designer wrote it and slices up all your images. It also outputs LESS, SASS, HAML, Slim, Jade and I think there are some other formats I may be forgetting.
Text is output as text. If you use a Google font, it automatically links the fonts in for you.
It does not use absolute positioning so if you modify things like text and it grows taller or shrinks shorter, other items will be positioned properly (initially we did it with absolute positioning but later I figured out an algorithm to make it work the way it should, even with overlapping elements).
It's definitely not an easy problem to solve (hence why we've been working on it for over a year although not full time).
We've done some outputs now and the results are amazing.
I would link you to the website but it looks so bad right now that I don't want to show it. Anyways, we will launch in about a week so look for an announcement. If you have any questions about it, please leave a comment.
Sunny