The Iron Kingdoms has some of the best fluff of any setting I've ever seen. The art is gorgeous, the background is original, the setting descriptions are well-written, evocative and numerous, and the NPCs are full of personality.
It also has some of the worst crunch. The mechanika rules are nightmarish, statblock errors abound, balance is nowhere to be found, and none of the new rules follow either the conventions of the d20 system or an internal logic of their own.
Buy Iron Kingdoms material in the same way you might buy Spelljammer or Dark Sun material: as a great setting that as written doesn't actually work with 3.x. Looked at in that light, you really can't do any better. Looked at as a setting you can run with basic d20 knowledge and compatibility, like Scarred Lands, Warcraft or even Arcana Unearthed, it will seem frustrating.
Personally, I love the IK and play in it at the drop of a hat. DMing it would be a much more daunting task; honestly, I'd probably use some other system for it, like Silhouette, Conan, Grim Tales or just d20 Modern, since so much of the crunch needs conversion anyway.