[SpiralOcean]

My first reaction to Growl was a bit defensive. I didn't want to install something that was constantly interrupting me, but was more concerned that personal information was being sent to the developer of whatever application I was using.

I've since warmed up to Growl and now love it.

It's a third party app.
They spent time developing it and released it for free.
Other applications can hook into it's messaging system.
It can be configured to be non-obtrusive.

The main benefit for me is I get small status messages about what the application is doing.

Like, when a backup of the data is performed. It silently appears to let me know that my OF backup has just been performed, and then disappears.

A lot depends on the type of person you are. If you like the chatter of applications letting you know when something has been done that is not necessarily important to you, then you'll like Growl.

In the OmniFocus example, most people just trust that the backup of their data is happening. I trust it as well, but it's reassuring when I see the Growl message saying that my OF data has just been backed up. I don't need to do anything about it, and I know that it has happened.