The food I eat has been cooked almost exclusively on cast iron my entire life.
My mother had cast iron as I was growing up, and I've had cast iron since leaving home. I rarely need to season it, and if something does happen to stick I either use a little kosher salt and a scrub brush, or get the pan good and warm on the stove top and pour in a bit of water to deglaze it. It's very rare that I need to do either of the above.
It is possible for the oils to go rancid, but it has to be unused for a long time. Washing it with soap will strip the existing rancid oils and the piece can again be seasoned (which is why you normally don't use soap on cast iron). If the cast iron is used on a regular basis the oils won't go rancid.
Properly seasoned cast iron is extremely non-stick. I'll put mine up against any Teflon coated cookware for easy cleanup, and the health benefits are clear. Cast iron holds the heat for a very long time; I can often turn a burner off early and continue cooking for a while. Soups in the dutch oven will stay warm for a very long time.
I probably have 20 pieces of cast iron-skillets, griddles, dutch ovens, etc. Other than one piece of stainless steel, if it goes on or in the oven it's cast iron.