I bought an old 10" mitre saw at a yard sale, and use it with a 10" disc for cutting steel. It works well, and as I have only $30 invested, I don't really care too much about it. It has cut a good amount of steel and shows no signs of wear. The one advantage is that angle cuts are quick to set up. The only problem I find is that the swivel table gums up pretty fast with grit. Cutting aluminum should be easier. tape/cover up the gap around the swivel table to prevent the grit getting in though.
I should mention that I have a seperate saw for cutting wood, and could not bring myself to cut metal on it, ... bordering on abuse!