Dawf http://dawf.codeplex.com/ is a useful tool with one big issue. The replace audio only works if you leave clips on the timeline. Project media, subclips etc. lose the audio. Not sure if this is fixable, but if it is, that would be awesome.
I don't get it. I use Plural Eyes to sync multiple audio sources all the time, then I simply delete the "bad" audio tracks. What does DAWF add that I don't already have?