I've searched online; I have found lots of information around HOW to assign/remove tags, but very little around how people USE them. (that in itself might be the sign that not many people actually use them? :)
The best I could find is that some people use them for categorising work; e.g. "Final", "Research", "Draft", etc.
However, although this is a very legitimate way of using them, I feel that still doesn't use tags to their full extent - namely, the ability to have more than one tags attached to the same file. In the example above, a file is either 'draft' or 'final'. You can achieve the same result using nested folders, although that is different visually.
How do you use them? Or alternatively, can you suggest a link/site/blog that explains how they use them?