Hey Fusili & Jodie,
I agree, it's best to look at what's causing the noise (get to the root of the issue!).
I love the STP noise reduction feature because it can work really well.
However, recently I did a video project, and the recording (in a school classroom) was beset with hums and hisses and buzzing noises. When I listened back in my studio my heart sank as there was no way I as going to be able to go back and record again...
I used STP's features to pretty good effect, but there was still too much background noise, so i downloaded the demo for izotope RX (having used Soundsoap pro in the past which was adequate)...
It is amazing! The client is happy, But I don't ever want to be in the situation where the audio is so hissy again so I'm gonna invest in better mic's and field audio stuff and iZotope RX in the future ;-)
The demo is a 14 day trial, and can work as a stand alone or a set of plug-ins within Logic.
But most uses I think STP should be sufficient.