Land in an asteroid, don't roll 4 damage, take an action and shoot ?

Cross a debris and skip the stress token?

TIA

Correct. The downside is that you have to discard it to make it work, which means a: it only works once, and b: it anti-synergises with Integrated Astromech.

Unlike Dash, you can't choose not to ignore obstacles during the round you've activated it. I don't know if that's truly a downside though as it would very rarely be a useful thing to do.

It would almost never matter since also unlike Dash, you ignore them during combat as well.