Java is not needed. A frames-capable browser is not required, but is supported. This should be compatible with all browsers. Newest messages first. New messages are shown at the top, so you don't have to scroll down to see what people have said after your window is refreshed.
New messages are more obvious.
Messages which were sent since the last time your browser refreshed appear in a different style than normal text, letting you know immediately what's new and what's not. Sysop users, being registered users, are password protected. All sysop commands are invoked by simply entering the command from within chat. God users are identical to sysops, but they have the advantage of being able to see whispered messages. There's a pull-down menu you can use which contains the names of the people in the chat room.