While i haven't tried Iron Kingdoms using the Pathfinder rules, I will say that the rules play quite well with a number of systems, and settings. Part of the genius of Pathfinder is that, not only is it OGL compatable with nearly everything, they even go out of the way to give examples of play outside the standard swords and sorcery genre(s). (The Inner Sea Setting guide gives examples in the back section for exploring the worlds in the same system as Absolom as well as exploring other planes of existence.)
I myself have run several settings, both official, and homebrew under the standard of Pathfinder, including: Ravenloft (Swords and Sorcery edition), athas.org's Dark Sun homebrew, Colonial Gothic D20, as well as an improvised Planescape adventure arc.
Its pretty easy to take a setting, like Iron Kingdoms, which already bases much of its rules set in 3.x, it might take a thorough read through and a patch or two here and there, but one of the great parts of gaming is coming up with creative solutions for the game and adventure with your players. It gives them a vested interest in the outcome if they feel they've contributed.
Back on topic. Its much easier than you think, it may take a tweak here or there, but if you're already GM'ing...you've already had some time invested...
"When Fate taps you on the shoulder, you'd best pay attention. Unfortunately, she has the blasted habit of tapping you on the opposite shoulder, so that when you turn around she's actually on your other side, giggling like a schoolgirl. I hate that."