We have just published a white paper that explains the scalability limits of Team System Web Access 2008 power tool.
Download it at:
If you have more than 100 users using Web Access, you may want to take a look at the document to understand what these limits are and what you can do to improve the scalability. The white paper talks about the symptoms, limits, test results and workarounds.
You can contact me in case you have any questions or feedback.