Goliath with good stats for the Powerful Build trait, Large sized chain for reach and damage increase, feats as mentioned should be as viable as anything for a fighter all the way until Spellcasters dominate. At least I hope so. I am starting one soon.
As I think about it, the spiked chain is a cool option for a fighter instead of the "SEE ENEMY, SMASH ENEMY" mentality. Tripping and disarming are a nice change of pace. The reduced damage output is not a problem when you consider the overall impact of the weapon on a melee. The winner of the fight is the guy who takes all of the other guys hit points before losing all of his own. Armor class is the best way to reduce your hit point loss, but so is keeping the other guy out of melee reach. In the right situation, being able to utilize the full attack option while the other guy gets to use only a partial action to attack or use a ranged attack because he has to stand up every round, is a great way to make him bleed faster than you. Even without a high BAB, the improved trip let's you hit most things because it is a melee touch attack, then have a good chance to reduce his armor class, and you get another swing for damage, and to top it off it sets you up for a third attack when he stands up. You bleed slower, he bleeds faster. That equation works at all levels.
Notice I said "in the right situation." I am not planning to specialize exclusively in the chain. When my DM gets tired of seeing his bad guys on their buts, I will need a big sword to take out the ten legged huge undead behirs. As good as the spiked chain is, in the wrong situation, it is more useless them most weapons. Given the arguments on both sides, I would have to say the weapon is balanced. That being the case, I think it is going to be a fun alternative.