The only negative thing I have to say about Flatbox is that the footer area sometimes floats (doesn't stay at the bottom of the screen) if a page doesn't have enough content (it doesn't seem to do this with all computers/computer monitors), and I haven't yet uploaded a header image that doesn't get stretched (I'm not sure if this is because the theme stretches the header image to the screen size, or if this is because I'm uploading my image with the wrong dimensions).
Final Analysis: If you're looking for a simple theme that looks great and can be customized, check out flatbox.
The layout, look and feel of the theme is perfect for what I am doing. I'm able to deliver a functional MVP (Minimal Viable Product) with zero custom coding / modifications to the underlying style.css sheet. WP and the FlatBox theme have saved me tons of programming time - thank you!
This is one of those themes you are so thankful to have in your toolbox. When you're looking for "full-featured simplicity", Flatbox delivers.
Out of the box it offers just the right balance of features to get quality sites up and running without a great deal of fuss.