Well, for one if our IP gets null-routed due to HE abuse reports your site will stay online. A month or two ago Tommy was down for like 10 hours, and anyone with a dedicated IP didn't even notice the outage. Dedicated IPs also make SSL work on really old operating systems like Windows XP. If you try to go to https on a shared IP on Windows XP there is no way to display the site. It just doesn't work.