thanks for your appreciation.

Well, actually building the test cases tree on the server with so many items is not as easy as it may seem... and probably also rendering it is not such an easy task for the browser.

I have already worked on the performance side some time ago, with this ticket, http://trac-hacks.org/ticket/8869 , and it made things a lot better.

I think there is still one problem: the Test Manager tab page shows all test catalog and test cases together. These may be a lot of objects to load and display!
One solution may be to only show test catalogs, without test cases, in this page. This may be an option in trac.ini.
What do you think?

To speed up your Trac site now, anyway, you may create an alternative Home page for your test catalogs, linking to the top-level test catalogs.
Something like this:

= Test catalogs =
[wiki:TC_TT0 First test catalog]
[wiki:TC_TT4 Second test catalog]

Let me know if this helps.