I have used my “Second Passport” to travel to a country on a business trip where it would have been at the very least frowned upon to go there with a U.S. Passport.
I am working on getting the passport of an EU member which would open up additional doors for business travel.
The interesting thing with Canadian passport control is that they use the same technology as the US for reading passports, so when they scan my American passport, the immigration agent knows right away that I'm a dual citizen.
Our son is due in September, and I'm making sure to register his birth with the Canadian government to ensure his citizenship.