From: Seattle, WA
I'm not going to list the pluses of a static IP, but I will list the problems with a dynamic IP.
I have two dynamic IPs and I host my own domain names, DNS server, email server, web server, etc. When one of those IPs change, I have to modify my DNS entry for internic. It really sucks and for 2-3 days will not work. If you are doing anything for business, you can't afford to not have a static IP. That IP wont change on you and you shouldn't have any downtime because the IP changed.
From: Essex, England
What about using a service such as DYNU. I use it (its an NT service, runs in the background on NT, or as an app in 9x), it dynamically maps a web address (www.cableserver.co.uk in my case) to my dynamic IP. If my IP changes, it instantly updates its DNS servers.
Im not exactly sure how it works, as from my understanding the DNS change would have to propogate all around the internet (48 hours etc), but updates seem pretty instant. I think their DNS records are created so root DNS queries go to their DNS servers first, and dont cache the result.