Theres a [i]Test Server[/i] button located in the EQ2 patcher. Make sure you have enough space on your HDD as it basicly creates a copy of all your EQ2 files and uses those as the test server files to avoid tainting your original ones.
The test server is primarily used to test new and upcoming updates (duh). Its pretty cool to login and see whats to come. Also, i believe you can login right now and test the latest adventure pack in its BETA form.
Check the
www.eq2players.com forums for more info on that.