Tags for project notes & expenses

Tags are only being used with documents right now. We are contemplating layering tags into more places for better classification of items. For example, with project notes it would be nice to add categories like login, notes, tips, etc. We believe strongly that tags work better than categories because they are more free form and you don't manage them as much as categories. You avoid the "miscellaneous" category that is only good for the person categorizing the item. Not sure where it goes, add four tags.

This same tag mechanism could be used for expenses as well. Maybe it was travel, licensing, hosting, etc. This would allow for better categorization of expenses.

Thoughts? Would it make your life easier or add more complexity?