This question applies more in regulated environments.
We have our software requirements stored in Word documents an enterprise-wide CFR part 11-compliant document vault. These requirements are reviewed and approved by many organizations. Turns out that there are additional more detailed requirements which are needed to properly implement features and those are linked and managed within VS2010. We do traceability fairly manually (at this point) in an excel spreadsheet using the requirements from the Word documents with pointers to test cases which also live in the document vault. Again, there is quite a bit of review and approval on this part of the process. We haven't officially called these the "essential requirements" just yet, but it looks to me like they are. Software developers and testers are primarily involved in the writing, review and approval of the requirements and associated test cases which are being managed within VS2010. My question is: do others deal with layers of requirements and the associated traceability and how do you handle this?