The point of apps that turn off the startup sound: some of us have extremely loud stereo systems attached to our Macs. Some of us also shut our Macs down every evening, and have it start up automatically at 4am, to run backups, diagnostics, etc. Some of us have home offices, which would mean these daily startups would wake the cat, the people sleeping, and rattle the windows. So, for those of use with the above situations, a simple, free utility that silences the startup sound is exactly what we need.
True, we could remember to turn down our speaker set every evening before retiring. But who's really going to remember that, and why? And if you're relying on the startup bong to determine the health of your Mac, the least of your problems is going to be a sound or two.
There is no need to pay $15 for this app. On all my Macs, which are all running 10.4.3, I use the free StartupSound.prefPane which is tiny, stable and free. You can find it here: