In general, across all platforms, I actually think Facebook does an incredible job with their UI.
It's probably one of the most complicated applications most people ever use and yet it is used a huge amount and in some depth.
Every single time I use this control—and that's probably at least once a week—I click on 'Custom' first, then get confused by the dialog that appears, and have to hit Cancel.
I then look again and realise it's 'See all lists...' I need to use.
I then wonder why there's a divider between the two sections of the drop down when each selection is functionally similar and why it says something as confusingly dilute as 'See all lists...' anyway.
Facebook: please tweak this so that I don't make the same mistake every single time . It's beginning to make me feel really stupid.