I have used a spray on oven cleaner a couple times and it works great. I only clean the window, not the rest of the smoker and I rinse it off well. Don't think vaporized oven cleaner would do the meat much good. Try to wipe it down with a soapy paper towel when I turn off unit to prevent build up, but sometimes I forgets. Chiefwej is right, once it cools that stuff is tough! Then its time to call out the oven cleaner.
I just use Clorox Disinfectant Wipes, the ones in the plastic round tubes, takes a few but they work pretty good. If you do not have time to clean it while still warm when you do get time just turn it back on and let it come up to 110-120 degrees, shut it off and it seems to loosen all the smoke residue back up and makes cleaning easier. I have read the Mr Clean Magic Erasers work great but never seem to remember to get some while in the store.
I've used both Fantastik and something called Resolution degreaser. Both have worked pretty well. I found that it's best to try to use a light mist and enough to wet the surface, but not enough to run. If they sit on the gunk for a couple of minutes, the gunk wipes right off. But, to tell the truth, I'm done cleaning the window. It's getting too cold here. Either the window gets too cold, or if it's warm, I get too cold trying to clean it.
The racks and other removable internal stuff is another matter. I've found that a little Dawn and Oxi-clean, hot water, and a 45 minute soak in a properly sized storage tote (why yes, that was me in the storage aisle with the measuring tape) will allow the gunk and stains to wipe or rinse right off.
A can of Easy-Off oven cleaner makes the job really simple. I open the door wide open to the cool smoker, Spray cleaner liberally on the window and wait a few minutes. It foams up and you will see the grease running off the window as brown streaks. Come back in a few minutes and wipe it with paper towels and then rinse with the garden hose. Window is perfectly clean and clear. I only clean the window, not the rest of the smoker! Takes only a couple minutes and is super easy.
Single edge razor blade in one of those holder thingys and finish with Windex. Took maybe 5 min. Bearcarver told me about the Windex but mine hasn't been cleaned for a number of smokes. Razor blade takes 95% off. Windex cleaned the rest.