I think there is something very different about this "Code Orange," particularly since the standard for code orange today is a bit higher than it was several months ago. I also think that the LEO as coordinated through DHS is more in tune now than at any time since 09.11, and when they show signs of heightened concern, we need to be extra suspiscious, vigilent, cautious, etc., etc.
The fact that AQ hasn't used nukes or other WMD means nothing to me other than (a) they don't have them, yet; (b) they have them, but lack the logistics to use them at this time; (c) they have them and have decided for strategical reasons not to use them yet; or (d) they have tried to use them, but the attack was thwarted by LEO, DHS, our spooks, whatever.
As to why AQ would use jet planes and more conventional explosives as weapons if they in fact have WMD, my theory is two fold: Either AQ didn't have the weapons on 09.11 or lacked the logistical network to use them effectively; or they chose not to use them at the time because they don't have many and are saving the best for last. In other words, why use WMD on 09.11 when you can hijack a few airplanes and kill 3000 plus people -- a number which could have easily been ten times that amount if AQ had attacked the WTC an hour later that morning and crashed the planes into the middle of the towers rather than the upper floors. Jet planes are not as easy to hijack these days so AQ will use a different plan to obtain maximum death and destruction, which is why they may choose to use WMD at this time, because that may be all they have left.
In my view, AQ is not so much a terrorist organization as it is an army at war. The goal is not to terrorize, but to defeat the west and establish the Wasabi brand of Islam worldwide. An occassional car bomb, sniper attack, power outage, or airport shooting is not going to win the war when LEO can provide a less threatening explaination for the event. AQ will plan carefully and take their time between attacks so as to cause maximum death and destruction when the time is right. They used airplanes 09.11 because they could do so with relative ease. They may use WMD this time, because that's all they have left.
Lastly, I don't know whether these threatening internet posts are from one person or many, or whether the writers are members of AQ or AQ wannabees, or just kids looking for kicks or whether the purpose is to instill fear in the infidel or send messages to AQ cells. I do beleive, however, that the fact that AQ has not warned of attacks in the past is meaningless. The only thing worse than a catastophic attack in the USA would be advance warning of the attack and our inability to stop it.