Note: I haven't updated WeaponJuggler for WoW 2.0.
My attempt at a clean Weapon swap addon, upon believing that WeaponQuickSwap was broken after one of the patches (can't remember which one). As it turned out, my addon exhibited the same problem after spending numerous hours developing it (d'oh!). The problem turned out to be a change in the way Blizzard handled having the Alt key pressed down--and I had bound my "Equip Dagger" and "Equip Sword" macros to "Alt-D" and "Alt-S". Oh well. The fix was to switch to "Ctrl-D" and "Ctrl-S".
Then I still thought mine was still superior because it was cleaner code and relied on events to provide a purely asynchronous swap mechanism. However relying on game events turned out to be unreliable, making things really tough. And then... Blizzard nerfed weapon swaps, so I eventually abandoned WeaponJuggler. I still learned a lot writing it though, and there's probably something in there worth reusing. Please find it here.