The developer tells us that WhiteLine was born out of frustration for not being able to find a proper ‘minimal’ theme; they were all either ugly or incomplete. So he set out to build his own solution, with zero background in iPhone theming.
As for its looks, the black and white color scheme is a huge departure from the stock iOS UI design, so it might not be your cup of tea. But I really like it. From the 2D, see-through icons to the solid gray Notification Center, everything looks sharp.