I don't know how to package and deploy the final release other than by using MADDE (and I didn't get that working yet either, I have another thread on that).

What I mean is you can compile your project for Maemo inside QtCreator, as descibed in the original guide and then if you have your N900 connected to the PC via USB (with PCConnectivity running on your PC and Mad developer running on your device, just follow that guide exactly step by step for the setup) then after compilation has completed QtCreator will launch your app live on your device. You can then start and stop your app from within Qt creator on your PC, and interact with your app on the device. It's just a quick way to test your code is working ok before going through the process of packaging and deploying it properly.