I personally do not agree with the horrific nerfing of the spiked chain. However I will concede that a lot of people felt it was.
So here is my quick thought to a, not critical hit, nerf attack.
Heavy Chain, Spiked
25 gp - 1d6 - 2d4 ×2 - 10 lbs. - P - disarm, trip
A heavy spiked chain has reach, so you can strike opponents 10 feet away with it. In addition, unlike most other weapons with reach, it can be used against an adjacent foe.
You can make trip attacks with the chain. If you are tripped during your own trip attempt, you can drop the chain to avoid being tripped.
When using a spiked chain, you get a +2 bonus on opposed attack rolls made to disarm an opponent (including the roll to avoid being disarmed if such an attempt fails).
Light Chain, Spiked
25 gp - 1d3 - 1D6 - ×2 - 10 lbs. - P - disarm, trip
A spiked chain has reach, so you can strike opponents 10 feet away with it. In addition, unlike most other weapons with reach, it can be used against an adjacent foe.
When using a spiked chain, you get a +2 bonus on opposed attack rolls made to disarm an opponent (including the roll to avoid being disarmed if such an attempt fails).
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 for you.
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Sorry meant to give the light chain a weight of 6lbs
For me the biggest problem with regards to the Spiked Chain were the attacks of opportunity that the wielder would often gain.
Whilst reach weapons often get in more AoO then usual melee weapons they are offset by the fact that they cannot hit adjacent foes, but of course the Spiked Chain did not have that problem at all, making it a pleb killer when combined with Combat Reflexes.
Another suggestion to nerf but not kill off the flavour of the Spiked Chain would be to leave it stat-wise and reach-wise the same as it was in 3.5 but because it needs momentum, time and more work to use in combat, rule that it cannot be used to make any attacks of opportunity; solving it's biggest problem (AoO) but still allowing the reach for those that like it as it was.
Where'd that other thread go? This just came up. :)
My solution was that you only threaten to 5 feet, and provoke at 10 feet as if making a ranged attack.
While mine was to make it work like the whip and not threaten at all. I'm not bothering with the link Tejon's suggestion and mine plus some nay saying was all that was there.
I kind of liked the idea that someone suggested: you can either treat it as a normal reach weapon, or as a double weapon without reach, and you can switch back and forth from round to round.
My fix is to just use the 3.5 version, but, then, I never had a problem with the weapon as it was written. I guess if you've been having problems with it, then trying some complicated fix is a good idea. Maybe the non-threatening thing, I suppose, but I'd much sooner just wield a glaive and a spiked gauntlet than touch a spiked chain in that situation, myself.
IMHO spiked chain was fine the way it was, with the exception of too many abilities. Losing the weapon finesse evens this out. I don't care that they have a large threat range. Personally I think all exotic weapons should have this sort of unique ability in one fashion or another.
The idea of threatening 5ft but being able to make attacks out to 10ft is an interesting one. In the case of the aberrant sorcerer bloodline there's precedent. In that case your arms grow longer as you become more freakish, but mechanically it's very clear that you only threaten as a normal non-reach person would, but that you can make attacks out further.
THAT would have been interesting, to justify an Exotic Weapon Proficiency feat requirement.
Because the feats that made the spiked chain so abusable are now gone, there was no reason to change it i.e. Imp Trip no longer gives a free trip on knockdown (you need another feat for that).
However if the goal was to remove all weapons usable at reach and adjacent, the fix we have was a foolish one. Who would use a feat to fight with a short limp noodle with worse stats than a flail?
Two more reasonable fixes:
Simply make it a regular reach weapon.
Or, make the wielder decide at start of his turn if he'll be using it at reach or at adjacent and have that decision last until the start of his next turn. I'd personally simply use the stats of the light and heavy flail but have the two exotic weapons that grant the variable reach. Both would be two-handed, but you'd need to use the light version if you wanted finesse.
I kind of liked the idea that someone suggested: you can either treat it as a normal reach weapon, or as a double weapon without reach, and you can switch back and forth from round to round.
This is actually the best suggestion I've heard and also the most realistic in my martial arts experience. Same should also apply to the meteor hammer.
I also wish that the chain blade seen in the movie Ninja Assassin was in Pathfinder, a very utilitarian and usable weapon found in a very unrealistic (but fun) movie.