In my experience, cleaning the oven is a hideous job. The hideousness comes in the form of removing all traces of toxic oven cleaner from the oven. Scrubbing the roasted on black-brown chicken grease off of the oven walls is not so hard. It comes off with oven cleaner and a scrub pad. It's getting all the traces of the whole affair off out of the oven, so that it's actually safe to cook food in, that is life-sucking misery.
Now a word to the wise: Seattle Public Utilities, a resource for Seattle plumbers and homeowners, advises not to use an oven cleaner in a self-cleaning oven. I am writing specifically about cleaning an oven that does not self-clean. This should go without saying, but wear gloves, long sleeves that you don't mind ruining, and some kind of face protection. Be sure to ventilate the kitchen well when working with oven cleaner.
First of all, don't forget the broiler. If you have a broiler underneath your main oven, know that all of the waste water from your cleaning effort is going to drain down into it. Best advice: Save the broiler for last, but remember that it is there. Also remember to clean up the floor underneath the oven, where inevitably a puddle will form, in order to avoid a call to a tile contractor to regrout the kitchen floor. Also, remove the racks and clean them in the bath tub, or outside if you have a yard.
An oven cleaning expert I know, a working mother of six grown kids, gifted me with this advice: Open the kitchen window, and spray the oven with oven cleaner before you go to work. Let the nasty oven cleaner work its magic and hopefully off-gas all day while you are not home to suffer. Then come home and scrub all the gunk off at the end of the day.