A new feature today found in iOS 4.3 (beta) allows users to delete an app that is in the process of downloading.
With iOS 4.2.1, users have the ability to pause and resume downloads by tapping on the downloading app, but deleting the app in mid-download is a new function. This is a nice feature, mostly for the convenience, if you decide you do not want to the downloading app or if the app is frozen in mid-download.
To use the feature, first you must have iOS 4.3 installed. After that, when you are in the process of downloading an app, tap and hold on any app icon until the app icons begin to wiggle. Now, appearing over the downloading app, you will see an “x”. Once tapped and confirmed, the app download will be interrupted and deleted.