Meta Refresh chats are usually a bad idea. As you have no way to 'push' the chat text to users. This means you have to refresh at some given rate and depend on the user's browser to do the refresh properly and not to cache.
This makes it seem kinda kludgy and slow. The only way I know to make it seem better is to decrease the refresh rate to 1 second or so. This may kill your box though, unless you expect just a few people to use it.