I'm just getting started using the 9300 with GTD, and here's how I believe I'm going to go about it.
I've created an upgraded account with Backpackit.com - an excellent web tool that allows you to create multiple lists (with notes, images, files, etc.). Inherent in the Backpack setup is the ability to e-mail new To-Dos, Notes, and Files directly to each page (or, in my case, each contextual nextaction page). This allows one to add things to their inbox/lists remotely via the 9300's e-mail interface.
Additionally, you can configure reminders that are sent via e-mail or SMS. What's cool about this feature is two things: new SMS messages actually trigger an alarm on your 9300; and you can configure reminders to be e-mailed directly to another list within your system (if, for instance, you have a waitingfor item that could be accomplished only after a certain day, you can trigger that item to be automatically e-mailed to your nextaction list on the appropriate day).
Lastly, Backpack has a mobile version of its interface that is much speedier than the full site. You can review and manipulate all the data in your lists remotely via your 9300 browser quite effectively. After all, as good as Opera is on the 9300, transfer speeds can be a real pain.
Just some thoughts..