Luckily, I don't notice any of these artifacts!
How hard do you need to look to see this? I almost don't want to try looking for them... it might scar my impression of it.
Although, I have my screen set to shut off after 30s of inactivity and I've never left the screen on, unless watching a movie, with a still image for longer than maybe 4-5mins (reading articles, showing people stuff, etc.).
I've had the phone since December 8th (was so excited!) and I'm absolutely in love with the display. I thought I could handle iOS but... I moved from an iPhone 4S to the Nexus and I don't regret it, I hate that operating system.
Handed the iPhone off to my girlfriend and we're both the better for it.