When I created my Spiderip-hack, I've first used a slightly modified version of the IP-Banning function of vB2, but this was quite slow, so I tweak it (same tweak used for this 'hack') and it (online.php with the spiders listed there) was much faster.

And since were using a big list of banned IPs, I've applied it for IP-Banning as well. If you have a small forum with only a handful of banned IPs, you probably won't recognize any difference and a single user won't recognize a difference as well. But with a bigger amount of users and/or a big amount of banned IPs, you should recognize, that the serverload has been reduced.