If it's not one of those $10 special ones, you can do a great job with it. We had one that was our main oven for anything that fit into it until we replaced our stove (we got a dual oven stove where the second oven is the size of a large toaster oven, love it).

If the oven heats with top and bottom elements you may need to cover food to keep it from burning on top, but it heats up faster then a real oven, doesn't heat up the entire room, etc.

But the higher end ones that are well insulated do a great job as a small oven.