I'll join my voice to those that dislike doubleweapons.
To tell the truth, I loath them. Allowing silly fantasy weapon that defy physics is fine, some people like them. But making them super-Superior weapons, why?
To be fair, they are only completely out of wack for two case; Rogues and Tempest.
For a ranger, they only grant +1 to AC and the advantage of not needing two different weapon to keep pace in the magic item rat race. Probably a better deal than using two bastard sword IMO (also an eyebrow raising concept but at least one that is balanced) but not terribly unbalanced.
For a rogue; doublesword make Rapier obsolete! Why on earth would a rogue pick a rapier when a doublesword gives the same attack bonuses and damage but also give a +1 to AC! The idea that any min-maxer worth his salt seeking to increase his damage dice will bypass the rapier, a typical rogue weapon, and go for the doublesword makes me sick.
And the tempest ; Just forget it. What they seem to be trading in for their build is completely recuperated by using the doubleweapon. A tempest using two short sword seems balanced, one using a doubleweapon seems highly suspicious to me. At any rate, that one feat gives him a ludicrous boost in power!
I keep expecting some errata, but nothing yet has come down the pipe. I hope it's coming, they have errataed some much less problematic stuff.
My personal solution is removing the off-hand tag on the doubleweapon and the light blade tag on the doublesword. The weapon is still silly, but roughly balanced IMO without these feature.
or later 
when the MotP can be proposed. 
Gimme that Githyanki Silver Sword baby!! 
