Jesse Gallagher just tweeted this notes.ini setting (server, not client!). This will tune up you Admin client's performance as it will skip the "domino" directory of the server from scanning all the files put in there when opening the files tab. Thank you, Jesse for sharing it
ADMIN_CLIENT_SKIP_DOMINO=1
Place this line in your server's notes.ini at the bottom. Open the Admin Client and welcome the improved performance!