If you are making your application real-life-proof you will also have to deal with diminished or dropped connectivity. I already discussed how to detect the kind of connectivity your app is having at present.
But another real-life restriction stems from slower bandwidths available over cellular connections, especially if you have no 3G reception. Even Long of Scribd showed me this trick I am about to explain here. This enables you to artificially create a bottleneck on your connection so that you can test how the app behaves when only cellular bandwidth is available.
This helps you to see if your custom progress bar is showing nicely or possibly if your progressive image is indeed progressive. Also this might reveal synchronous URL loading operations that you should never ever do in production apps.