The twitter demo includes both an <iPhone View> and a <Desltop View>. When such an application is launched in a desktop browser, the server automatically serves the <Desltop View>, which if you check in the model, is empty. therefore when launched in a desktop browser, the view is blank. To override this behavior and view the <iPhone View> in the desktop browser you must follow the instructions in the last paragraph of stage 1, adding the iPhone.html to the url.
Regarding the Sales Demo, the downloads contained, by mistake a local copy of iphone.html in the web folder, overriding the default one included in the platform, and that file had the radio-buttons removed. I've removed this file and updated the downloads.
The problem regarding data not being displayed seems to be connected with bug #565.
For best results, use the Firefox browser..