Dunno. I imagine it could be pretty effective against buildings and metal extractors and stuff. Pretty good troll move. Not an overly competitive move.
it does damage, and the unit is on an air layer. Ergo, if you have no anti air, it can cause damage uncontested do it early game, easily defeat unprotected establishments.
Actually, their default interaction with enemies have been for the longest time "reclaim". Since a tournament occured where someone recorded a player repairing an enemy.
4 fireflies are cheaper, much faster, provide better vision and should deal more damage against most units (such as a T1 tank) than an air fabricator. With that said, neither of them are good at dealing damage, and I'm glad they aren't, because that would be silly.
I have used construction aircraft to take out several scouts and small groups that have no AA cover. Works about as well as the uber cannon.
i had a guy rush me with air fabbers, by building crap-turrets right on top of me. by that time however, i was long gone, having colonized all of the moons. even so, i was all like "....really?" i beat him in that same game by slamming him with 25 nukes at once.
I remember a long time ago I played a random match 10-man FFA, and I decided that instead of actually attacking with regular units, I would build around a hundred air factories and spam Air Fabbers into oblivion. I actually got pretty far until this one guy got Levelers; this was at the time when tanks could shoot down Aircraft with near impunity, especially considering that Air Fabbers would fly down to ground level to reclaim stuff. Eventually, after around two hours of this fuckery I decided to just have the Air Fabbers build a ring of 5-second Holkins and Catapults and laugh like an idiot.
For combat units, attack is the default click as well. Would be nice if they had a different set of clicks for allied units. I imagine this is better though for the sake of diplomacy. You wouldn't want an enemy you can't click to attack, over a ally you can.