OSPF -vs- ISIS

All, Can anyone point me to information on what the top N service providers are using for their IGP? I'm trying to build a case for switching from OSPF to IS-IS. Those on this list who are currently running IS-IS, do you find better scalability and stability running IS-IS than OSPF? I understand that this question is a lot more complex than a simple yes or no since factors like design and routing policy will certainly affect the protocols behavior. Any insights or experiences that you can share would be most helpful. Thanks, Daniel Evans Alltel Communications