As I mentioned earlier, I love Remember the Milk. I struggled internally with paying (admittedly a measly $25 for something I truly value) for the premium service in order to use the iPhone app. I even ditched it for about a week or two in favor of Google Tasks because they had a web app that worked well and it integrated with Gmail. But a few of the features in RTM were a bit better overall and it is more intuitive in the critical task addition area, so I moved back.
I found the app that rocks it. It’s called Milpon (App Store link). It’s built using the RTM API and is free in the app store. The best part: it looks and acts exactly like RTM does. I love it. Problem solved.