EMP's are nifty little things, the problem is you can harden and shield devices from them, and although expensive, optical circuits can be developed too. It'll still do a lot of damage though, a lot of hardware currently in use probably wouldnt stand up to it, let alone ordinary equipment.
Reportedly they can also be lethal at very short range because of explosion and inductive heating effects.
The real problem is modern wars seem to be of the army vs low-tech insurgent type, emp's would be useless there.
I'm all for spraying aphrodesiacs all over iraq though.