Damn, Twan didnt spam his auto-submitter for his blogs...that must be a first
In my opinion, blog directories that sort on traffic in are nothing but large top lists. The big difference being is that there is no way to figure out what it takes TO make it onto the top of the blog directory. No information on if or when the count resets, how much traffic you need to send to stay on top, etc.
Twan's directories will send traffic provided you are able to stay near the top. Otherwise after about three days the traffic falls off drasticly.