I dual-booted Mint on my 2011 MBA the other week and it was a nasty experience. I feel like Linux users have low standards, or maybe I've been away too long. Here's four things I found immediately:

1. The fans don't automatically react to temperature without a background daemon (?!).

2. Multi-touch trackpad support is terrible. The default synaptic driver can't handle you resting your thumb on the bottom of the trackpad. The alternative driver doesn't support momentum scrolling (and is still a bit shit). At least palm detection has been solved; well done Linux, it only took you 10 years.

3. It cannot seem to handle using left Alt as a third-level activator (e.g. for # key on EU keyboards) at the same time as actually letting you /use/ your Alt key (e.g. for activating menus). I think I eventually solved this, but how hard should it be?!

4. As others have mentioned; battery life.

I was impressed that sleep, audio, wifi and display brightness all worked out of the box though. Progress, eh?