I remember people on an extremely distracting forum using it, ultimately it doesn't work. Those same people are still spending a lot of time on that forum, they've stopped turning it on.
Also worth noting, RescueTime has a "Get Focused" feature that blocks any sites that you have marked as unproductive (for a specified number of minutes).
Hadn't seen that, only a pay for app (and I'm cheap :))! Anyway, Focus is tailored perfectly for me, hope some other people can find use out of it too.
Edit: Clarification (I'm sorry I can't reply to your comment, it won't let me), I meant I had only seen a pay for app and not this one.
Edit 2: (reply to comment also) also doesn't appear to have exceptions, maybe I'm wrong.
I remember people on an extremely distracting forum using it, ultimately it doesn't work. Those same people are still spending a lot of time on that forum, they've stopped turning it on.