I installed those addons and configured Akismet. I am still getting 100 or so registers a day from evil users. In fact when I made my post the other day I had around 7000 users, today I have almost 9000. So it is being hammered by spam bots.
I'm curious as well if there is a simple way to clean these users out. Even if I am able to solve the problem of spam bot users I still have 8500 users who are illegitimate. This sfs.php script can find them but provides no easy way to delete them except one by one.