With the imminent release of Team Spec Juan Perez has released a bunch of videos describing how you can use Team Spec to manage requirements in conjunction with Team System.
I've been testing Team Spec and it seems that will be a tool that can bridge the gap that currently exists with managements requirement in Team System. It's a word add-on that will allow you to write specifications directly in Word and create work items directly from that information. You can then change information in both systems and have the information automatically automatically synchronized by the tool, making sure your specification is always up to date (and vice versa)
The opposite is also true, it can import information directly from work items to Word documents, not only making it a tool capable of managing requirements but will allow you to write other type of documents that needs information from work items. For example, it can be used to easily write status reports and have the information about the state of work items easily refreshed with the click of a button.
Looking forward for the release of version 1.0