If your app is not completing the download, I would try the troubleshooting steps here:
iOS: Troubleshooting applications purchased from the App Store
Specifically, steps 5 and 6:
Hold the Sleep/Wake button until "slide to power off" appears. Slide to power off your device. When it is off, press the Sleep/Wake button to turn it back on.
Remove the application from your device and reinstall it.
- Touch and hold any application icon on the Home Screen until the icons start to wiggle.
- Tap the "x" in the corner of the application you want to delete.
- Tap Delete to remove the application and all of its data from your device.
- Press the Home button.
- Go to the App Store.
- Search for the application and then download it again.
Even though the app has not finished installing, step 6 should still allow you to delete the icon with the progress bar and try again.