You wont notice it if you use your phone. Retention happens when the screen is on all day showing a static image that doesn't change. On a macbook that would mean the apple logo for sure would burn in. Hell, even on my non-oled lcd monitors they're burning in even though they're not supposed to.
Even with pixel shifting you can still get retention too, so that's not really an option right now. I'm hopeful some company in the future will come up with a way to prevent it altogether - but it's going to have to be some kind of new screen tech.
I don't leave my screen on the same image all day. It's on about as much as my phone. I turn it off if I'm not actively using it. This is my point. If I can have it on my phone, I should be able to have it on my desktop.
Even with pixel shifting you can still get retention too, so that's not really an option right now. I'm hopeful some company in the future will come up with a way to prevent it altogether - but it's going to have to be some kind of new screen tech.