Felton says the main lesson he learned from the experience of designing and iterating Timeline is that “Photoshop lies.” “You can come into a meeting with a very beautiful comp and it’s like, ‘Oh yes, we should do it that way,’” he says. “But you’re never going to know if you can do it that way until you pump in the real data and live with it for days or weeks.” [emphasis mine]
This is why I always try to get real content to design with – and even that’s never a guarantee it’ll work out once the project starts getting real. It’s easy to make an attractive UI in Photoshop, but there’s a reason a lot of pretty designs fall apart once they get built.
It’s time to leave behind the rigid separation between designers and developers: the sooner you can move from concept to some form of implementation, the faster flaws become apparent so you can begin fixing them.