I use the oven
feature of my 6000 series Origo periodically, on average 1x per month. Overall, it is easy to operate, including filling the alcohol canisters.
compartment is wider than it is deep, maybe 12-14" x 7-8". You have to split a 12" round pizza in half to cook. Height is adequate.
A thick stainless shelf over the burner serves as a diffuser for the flame. I have had no trouble reaching 350-375-400 deg oven
temps. You have to fiddle with the temperature "control" a bit to ensure a consistent temp.
The only downside is that it takes longer, on average, to heat the oven
to temp than a similar sized propane fueled oven. I find that I will get 2-3 hours of cooking per canister fill.
Baked Ziti, Pizzas, Refrigerated Rolls, Frozen Chicken Parm and Cinnamon Buns have all come out of our oven this year with good results.
I am curious, if you are going to the expense of adding the oven, why not go propane?