That depends. MacBook Air 2012 11 inch is one of the best machines I have ever seen for Linux. In fact Linus himself used one for some time, which he praised. It's a very standard Ivy Bridge machine, also extremely silent.
Everything just works with a stock kernel. Only minor caveat is that the wireless card has bad range. But also in Mac OS, so not sure this is a driver fault. Easy to fix, I use an external Atheros from Alfa which has incredible range and is great for pen-testing.
Apart from that, the only annoyance is that the battery does not emit ACPI discharge events. But very few laptops do this, apart from some ThinkPads. (I would love to know which do! These are really useful to set up udev sleep rules instead of polling the battery on a tiling window manager & no-desktop-environment setup, but it is a feature rarely documented.)