Apparently, unless you get an engineer that specializes in ICF construction, a regular engineer will cause many delays and possibly cost you money. Due to the price difference ($6,000 vs. $500), we went with a regular engineer, the un-knowing kind.
The engineer first thought everything was okay, then realized that we have a 2nd floor exterior wall ending right where our 1st floor kitchen begins. This caused him great distress. Woody, who has built with ICF many times, went round and round with the engineer about this. He knew he could make it work, and finally, after much argument and back-and-forth, he convinced the engineer and got him to sign off on our plans.
It would undoubtedly have been easier on him & on us if we could have found a reasonably priced engineer who was at least somewhat familiar with ICF construction, but such is life, and such are the risks entailed with building with a strange, new form of construction.