Well, Iowa isn't known for having a good business climate in general and for taxes it has one of the worst in the nation. This gimmick only applies to the state capital gains tax for 10 year old assets (the details get complicated there) and isn't likely to make it significantly more attractive for startups.

Maybe it's for farms and the like.... In general Iowa strikes me as a state for farming and big companies, but I live at the other end of Missouri from it so my opinion on it isn't very informed.