One major difference is that the enemy is not supported by a major power able to send them all manner of advanced and heavy weapons. Up until now, the Iraqi enemies have made use of the mountains of ammunition buried all over Iraq left over from the Saddam regime. And according to Strategypage, the enemy is Iraq is running out of Saddam's arsenal to make bombs:
Terrorists in Iraq appear to be running short of pilfered (from Saddam’s ammo dumps) artillery shells and explosives. Home made explosives are increasingly being used for roadside bombs. ...
The resort to improvised explosives for their bombs means the bombs have less power, and cause fewer injuries. The explosives shortage is largely a result of two years of American and Iraqi troops tracking down Saddam’s lost shells and explosives.
I had mentioned long ago that it seemed like guarding the border wasn't a high priority task for us since the foreign jihadis are few in number and because the enemy did not need a huge supply source to keep fighting because of the locally found arms. This is counter-intuitive, really, since cutting off insurgents from outside support is important as a general rule.
But not in Iraq's case. Guarding the border to stop a small number of men that our troops couldn't distinguish from locals and small amounts of weapons to fill in gaps in what was available locally would have been a waste of troops better utilized elsewhere.
It is a good sign that the enemy is not apparently being supplied from Iran or Syria in quantities large enough to prevent the enemy from resorting to the anarchists' cookbook for IEDs.
As Iraqi forces come on line and border posts are built, they may well be able to put a real crimp in the enemy if the enemy ever has to rely on imported arms and ammunition.