Well, I wasn't thinking for trips or anything like that, just the added utility of having reach and being able to attack adjacent. Most of the time when someone closes with you, you're going to get an AoO. Then if they try to withdraw, they'll provoke again.
It's not so much that as no one's tried the spiked chain since this rule came into play because spiked chains in Pathfinder don't have reach.
Chain, Spiked - 25 gp, 1d6, 2d4, ×2, 10 lbs., P, disarm, trip
Benefit: You can use the Weapon Finesse feat to apply your Dexterity modifier instead of your Strength modifier to attack rolls with a spiked chain sized for you, even though it isn't a light weapon.
As long as that's not nerfed, then we should be good to go.