Growl has a 5 Star rating on VersionTracker.com, but there are problems.
From one of our own -
mdnky
Bob,
We might want to issue a warning to others about Growl. Seems they have a major issue with their installer right now. I wound up in single-user mode hell immediately after installing it a few days ago, and I've talked with 3 other people who had the same thing happen within the past 2 weeks. In each case, the only fix was a reinstall of OS X. The issue was confirmed on another 'test-box' machine I have running Panther.
I just contacted their developer about the problem, waiting to hear back from them.
Heard back;
No problem. Karl replied to me, said they'll be releasing (or, were planning to release) 0.6 on Sunday. They weren't aware of any issues, but they're looking into it.
It seems the problem relates to the user account which installed it. Unfortunately, I used the only account setup on my computer at the time, so I was screwed royally.