Single axis (Z) in 2.2 and older.
That does suck.
That means you can't use the triggers as buttons, as many games like to. For example, a game in which left trigger is "aim" and right trigger is "fire". The problem is because if both triggers are pressed at once, they cancel each other out, and report a 0 (neutral) axis value, the same as if neither are pressed.
I was worried that might be the case. I once read that you need to use XInput to properly detect each trigger separately, although I can't verify that for certain.