I want to get a MacBook Air, but people seem to be criticizing its screen. So, I thought that if I compare it to my current laptop's screen, I might get an idea of how good it is. I own an Acer Aspire 8930g with an 18.4-inch High-Definition CineCrystal widescreen display with a dimension of 1920 x 1080. How well is this compared to MacBook Air's screen? (E.g how do you calculate pixels per inch?) Thanks in regards.