Sitecore 6.6 (Update 4).
MaxMind has an option for a Sitecore-specific lookup service that integrates with DMS. MaxMind also has some more generic web services.
Can the 'generic' web services be used in conjunction with Sitecore/DMS or am I limited to using the Sitecore-specific version? If there is no limitation, what reasons should I have for going with the Sitecore-specific version since it is more expensive.
Thanks!
Sitecore DMS uses MaxMind web services by default. There is a MaxMindProvider class in the Sitecore DMS which extends LookupProviderBase class and gathers the information about the visitors in a way which fits well with Sitecore approach.
I assume that MaxMind services for Sitecore are more expensive (I haven't checked it, but this is what you've written in the question) cause they are prepared for the Sitecore specifically and you don't need to do any coding to enable them - there are out of the box with clean Sitecore DMS installation.
Still you can use your own provider for the GeoIP data and implement it in your own way, e.g. using the standard MaxMind services.