Best way to dump a dedicated server provider when you have to change IP addresses to do it.
If I was not reliant on their IP addresses I would drop them in a heartbeat.
Changing providers would mean moving a bunch of VPS servers and changing IP addresses. Besides being a hassle, especially for what we do, it tends to cause cancellations.
This is not just web hosting. So it's not just a matter of customers changing their DNS.
We don't have our own IP's and that is not likely to be an option for us until IPv6 is more widespread.