I voted powerful on this feat, but the reality is that this one depends heavily on how "honest" your DM is with monster intelligence and monster knowledge. I have a player with this feat, and it'd be really easy to just not charge him and avoid the attack of opportunity, but I have to consciously stop myself and think, "Ok, this orc/troll/giant would probably be charging at this point, because it shouldn't have any idea that charging would be BAD."
If your DM actually has things charge you, it can be great. Grab a guisarme or spiked chain to knock em down so that they can't even hit you. In the special circumstances when setting a weapon for a charge can be helpful, this is also nice for that.
If you're using Psionics, the Stand Still feat is helpful as well.
