yup, i manually deleted about 10 users last night.
i have put new registrations on moderation, which means I have to approve their registration before they can post. I have to search each email against spam lists.
The thing is, the spam user joins and doesn't post right away. It sits for a few days, then posts, which makes them harder to find. They have also found ways around human verification codes (the graphic letters that you have to type in)