It will require a mind-set adjust on the part of you and your players. The classes are powerful -- very powerful -- to make up for the lack of magic. Someone around here has a great sig about not being your magic items... so very true in Iron Heroes.
The combats are (or at least, can be with the right group) very cinematic. Make sure to use lots of action zones and fun options in combat -- they really emphasize the differences between IH and normal D&D. Skill stunts should also be frequently seen -- make sure to use them against your players frequently so they get the idea. If you're more of a friendly DM, you could just have a starter session that uses a lot of them or recommend them early on.
Also, something from behind the screen -- Villain classes. Learn them, live them, love them. They make your life *so* much easier than trying to keep half a dozen token pools straight. If, for some reason, you want to run a villain with a token pool -- a BBEG or an important minion -- then try and lay out his actions ahead of time so you don't have to juggle tokens or look at options during the fight.
Make no mistake -- your preperation time as GM will go up at first. The investment, IMO, is worth it. I ran an Iron Heroes game from 1st through 15th/16th level and had a blast with it.
The only real concerns I can mention:
1) The Arcanist is terrible. Use one of the many variants on the net -- I particularly like using the True Sorcery book version, if you have that book.
2) Be prepared -- especially at higher levels -- for the sheer damage output of the Heroes. They might seem weak without all the magic gagdets, but a high level ANYTHING in IH can put out some amazing damage. Archers are especially nasty, in my experience.
3) There is little to no healing, except out of combat. With a couple of exceptions, these characters have X HP and that's it. So long, brutal, meat-grinder combats are tougher for the IH party than a normal D&D party. On the flip side, give them a half-hour to rest and they're ready to go again -- no worries about 10 spells a day and then rest.
Just a few thoughts. I really enjoyed running IH and hope you do as well.