My favorite thing about the air vents is that when the Macbook is in use (opened), the backs of the keyboard and display close in against the vents, creating a natural barrier to prevent most things (like bed sheets) from blocking the vents.

It seems really minor, but it's seriously prevented my Macbook from overheating probably dozens of times by now. I can't say the same for my PC, which has the flat ventilation panel on the side and has been killed by bedsheets many times.

A minor detail, but a really clever one. I like it.