I have been using this on the iPhone previously and now on the HTC Hero. I paid for the Pro version a few months back as I wanted to keep using the iPhone application. You can trial it on the iPhone but it expires after a while unless you sign up for the $18 a year Pro version. There is also a nice version available for Android and I’m fairly sure but not 100% certain that it is free whether you are a Pro user or not.
The interface on both is quite nice although I think the Android version just edges it, changing existing todos is easier and quicker on Android whereas it is a bit too convoluted on the iPhone app. The best thing is that both version sync directly with the RTM website therefore it does not matter whether I enter new stuff on the website or either device as all three can be kept in sync via wifi. I’d love to get a version for the Palm Pre but the way things are going that would be unlikely so in the meantime will continue using Fliq Notes from MarkSpace.
Having said that, the website interface is not good and it took me ages to work my way around it, trying to fathom how to edit stuff. Adding new todos is easy enough and with the “smart” system in place you can enter new tasks quickly. For example, entering “Clean kitchen Friday” gets translated into a task for the next Friday with the date added.