It was a pain in the ass having to use up a slot in my team in standard to deal with inconsistent. Doing it in a fast-paced metagame where a single mistake can mean losing the entire battle, like ubers? No thank you.
I say to just have a blanket ban on the ability, and prevent it from being used in any tier, like OHKO moves and Evasion moves.
An example is:
I started an ubers tourney on the PO server yesterday. The semi-finals, someone was beating his opponent. The opponent sends in an inconsistent Pokemon and sweeps.
Having an ability like that is hardly "creating a desirable metagame".
so yeah, there's my two cents