It is important to bear in mind that no ordinary users have administrative rights on the systems I manage.
All systems management and maintenance is carried out through a separate Admin account. In order for the users to do their work they need to be logged into their own accounts, hence the need to abort the download(s) being run under the Admin account.
Even if I were stupid enough to allow users administrative rights, the performance impact on the ability to access work over the network with such a large file downloading in the background would just result in a lot of severely cheesed off users.
I must admit, I'm not looking forward to the same scenario with Mountain Lion if Apple is going to persist with delivery of OSX and large applications and updates through the App Store. 😟