My interpretation of the double sword (invalidated by Wizards) was that one end counts as a Heavy Blade and the other counts as Off-Hand, Light Blade - that is, even though it's symmetrical, you make strong slashing attacks with your stronger hand and light, defensive movements with your off hand, so whichever end you happen to be holding in your off hand is a Light Blade.
BTW, I saw a house rule on the Homebrew forum here that I quite like - for players that want to become masters of the Quarterstaff, ban all double weapons and then add a feat that turns the Quarterstaff into a d8/d8 double weapon. d8/d8 isn't too unbalancing, and losing all the other double weapons makes this use of the Quarterstaff pretty unique and cool. (Which is good because I understand it doesn't get much love in AV or Martial Power, and it's an iconic weapon!!)
If we do end up banning double weapons, I'll probably propose this as a house rule. Do we have a policy on proposing house rules that aren't in published products?