I’m glad we are starting to seriously engage Iran:

The Bush administration has authorized the U.S. military to kill or capture Iranian operatives inside Iraq as part of an aggressive new strategy to weaken Tehran’s influence across the Middle East and compel it to give up its nuclear program, according to government and counterterrorism officials with direct knowledge of the effort.
For more than a year, U.S. forces in Iraq have secretly detained dozens of suspected Iranian agents, holding them for three to four days at a time. The “catch and release” policy was designed to avoid escalating tensions with Iran and yet intimidate its emissaries. U.S. forces collected DNA samples from some of the Iranians without their knowledge, subjected others to retina scans, and fingerprinted and photographed all of them before letting them go.
Last summer, however, senior administration officials decided that a more confrontational approach was necessary, as Iran’s regional influence grew and U.S. efforts to isolate Tehran appeared to be failing. The country’s nuclear work was advancing, U.S. allies were resisting robust sanctions against the Tehran government, and Iran was aggravating sectarian violence in Iraq.
“There were no costs for the Iranians,” said one senior administration official. “They are hurting our mission in Iraq, and we were bending over backwards not to fight back.”

In a shamed based culture, “bending over backwards” is seen as a sign of weakness and it’s now wonder Iran has continued to sow discord in the region. They have not paid a price yet, wait until they do. Maybe they’ll pull out or maybe they’ll escalate. Either way, if we are killing them, then one less soldier to fight if we ever have to take on Iran.
I know that some doubt that Iran is involved but:

Gen. Michael V. Hayden, the director of the CIA, told the Senate recently that the amount of Iranian-supplied materiel used against U.S. troops in Iraq “has been quite striking.”