Our convection/microwave eliminates most of our need for the oven. So I guess it depends on what you use your big oven for--if it's broiling, you're better off with a toaster oven, but if it's baking, you can't beat a convection/microwave.
We're debating on whether or not to bring up a toaster next year. This year we buttered bread on both sides and then toasted it in the cast iron pan. It works fine. I have to weigh a little extra convenience with the idea of another gadget in the kitchen.