No one knows.
Iron Heart surge is easily the biggest question mark in an otherwise-stellar book, worded very confusingly and plagued by nonsensical customer service rulings (that imply, for example, that it could turn off the sun). The errata for Tome of Battle gets just three entries in before being overwritten by the errata to Complete Mage (seriously; it’s still on Wizards’ site that way), so that’s no help.
Thus, most DMs are uncomfortable with the wording of Iron Heart surge. It's an uncomfortable thing, with very little certain except that its literal meaning isn’t very helpful. Clarifying it is necessary in any group before it can be used.
The “measured in rounds” interpretation is one I find absurd, personally. The idea behind the wording, as I see it, is to try to prevent it from covering Instantaneous effects. Maybe also Permanent and Concentration-based effects. Stuff that lasts “until XYZ.” But the unit of measure used should really never be important. Would he really allow it to affect something that lasts “10 rounds/level” but not one that lasts “1 minute/level”? I think that’s a little silly.
Ultimately, the maneuver appears to be a reference to all the times Conan shouted “By CROOOMMMM!!” to break free of something. Personally, that is exactly how I run it: anything it seems like Conan could break free of, the initiator can. I even allow it to end things that would otherwise prevent the initiator from acting, like stun, paralysis, and mind control. I handle AoEs by saying the initiator is immune to the ongoing emanation for the rest of his turn, so he can move out of it.
