I have Soundsoap and Adobe Audition which also has the noise reduction thingy bundled in. I like them both but when I was shopping around, I think my expectations were too high. I find them effective at removing very low level noise any more than that, it starts to take away first from the ambiance, then the highs and then becomes noticably worse than what you started out with.They both do a decent job removing predictable faint sounds. By that I mean like that faint hiss from the furnace ducts or the pc fan but only if the noise source is very faint.
Now that I have a finished work space, I don't have noise issues but here's how I used to use it...I would get the mics set up and finalize all the positioning and levels, start the tracks rolling and take a 20 second silent sample before the performance and then another 20 seconds or so at the end.
Both of the products I've used before allow you to take a snap shot of the room noise. You then use these snapshots to go back and clean out the desired recording. The less noise reduction impact you impose the better. As I mentioned before, the deeper you take the reduction effort, the more damage you do to the recording. I also found that this was more effective when close micing with small directional mics as it quickly tears down the sound in your ambiance mics.
For performance/people noises (chairs creeking, clothes rustling, lip smacks), I prefer to deep edit by hand...for this I use Adobe Audition.
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