I'm going to advocate having saved searches on the iPhone because it would arguably be the most useful feature of the iPhone app.
Many people only spend their time in one view, and having to tap 4 times to get to another view, say, from your "Homework" folder to your "home" context, is cumbersome. Not to mention the 5-10 seconds you spend switching. It would be much easier if you could just have a list of all your custom searches.