In an attempt to forestall any extra threadjacking in mercop's Tactical Pen thread, I would like to hear people's opinions on this subject. Feel free to be a bit in-depth into your thought process, please, as this will hopefully keep things from the "Oh yeah?!?" "Yeah!" "Oh yeah?!?" "Yeah!" "Oh yeah?!?"...that they can devolve into.
My take on pain compliance techniques is that they are an initial-aggression forceful deescalation attempt and not at the expense of other techniques being viable if they prove necessary.
Take the initial stereotypical push or grab in a bar for instance. You could then meld into the push or grab and go for a pain compliance technique that disrupts the assailant's base in an attempt to let them know that their actions are not cool. You're trying to be nice and not let things get out of hand here before you take your leave of the situation.
Now, if the assailant is already in full-on Rock-em', Sock-em' Robots or gets free of your initial attempt at controlling them then a different option should definitely be considered. People on adrenaline don't respond well to pain so an attempt to gain compliance from an obviously already very irate person with nothing but the very thing that adrenaline suppresses is probably not the Chinese way to long life, or to not getting your nose mashed. As most pain compliance techniques have a base disruption element, these techniques should be counted on only for this secondary effect in these situations.
Since I've already discussed unarmed situations then I hope it's obvious that armed situations have the same circumstances for pain compliance technique use as an already irate assailant. You can still use them, most pain compliance techniques also include a base disruption element as mentioned before, but only for this secondary effect. In such situations I strongly advise that you swap from a compliance technique to a destructive technique that will remove a tool from your assailant's arsenal, the compression lock being pretty much my go-to technique for such situations if I can get to it. Simply dumping them on their side/back and doing a full-on knee drop on their head and/or floaters is a close second favorite.