Hi sueds, thanks for the questions. You do understand correctly: ContentTracker allows you to micro-manage your content, but it will not provide any faster loading than the default ContentManager.
It overrides ContentManager's protected ReadAsset<T> method which will get called every time an asset is read from disk. This means that when you call Load<Model>(...), the ContentTracker knows that your Model references various Texture and Effect
objects (because internally ReadAsset is called on them) and allows you to interrogate these relationships. It also needs this information to provide the individual content item removal feature: For example, when you remove Model A, it will only remove it's
textures and effects if they are not referenced by any other models. This is called reference counting.
As for the threaded loading feature, this is not unique to ContentTracker. Many games will use ContentManager to load their content on a seperate thread. The real feature is when you combine it with individual content removal. The idea (as shown in the demo)
is that you can have a world that continuously streams it's content from disk, whilst also continuosly removing content that is no longer needed. To get the same effect with ContentManager, you'd need to wrap each world chunk in it's own ContentManager and
call Unload() to remove it, but this would also mean that any world chunks could not share their assets - if they wanted the same texture they'd have to each have a copy in memory.
ContentTracker does lend itself for use in an editor (on windows), not so much because of the threaded loading but because of the individual asset removal, and another feature: Source Asset Loading. On windows, this allows you to bypass the XNB files altogether
and directly read X file models, Xml files and Textures from disk.
If you want to read more about the internal workings of ContentTracker, the article on ziggyware is the best bet (http://www.ziggyware.com/readarticle.php?article_id=231).
Feel free to ask any more questions you have about ContentTracker.