But isn't the environment itself just as important?
What if you're using a DLL which already runs in an isolated environment and therefor blocks certain system and function calls? The DLL might contain certain bugs, but its impact would be quite different on both environments. So I can't help wonder if you're not effectively slowing things down. While you might be able to spot bugs more quickly it also means you'd have to test them in the original environment as well so that you can rule out flaws in the testing itself and determine their true impact.