I've been trying hard to get too involved with the detail of ADFS and Claims authentication, but I've not been able to avoid it completely (though as an aside, maybe I should try and adhere to the MCT renewal perspective that believes you cannot be an expert in more than one of Dynamics, Development, or IT Professional).
One issue I got involved is that the Crm Email Router can end up continually crashing if it can't connect to ADFS. This is a significant server stability problem, as the Dr Waston errors can cause the server to be compute bound, taking resources from other services. The symptom is a lot of errors in the event log like 'The authentication endpoint Username was not found on the configured Secure Token Service'. One consideration is whether you have the endpoint configured in ADFS (see http://www.powerobjects.com/blog/2011/06/22/error-with-crm-2011-adfs-and-email-router/ for an example), but another consideration is service dependencies.
In most environments, ADFS would run on a different server from the Crm Email Router, but in smaller or test environments they may run on the same machine. This causes a problem, as the ADFS service is set by default for a delayed start, whereas the Crm Email Router service is not. Therefore the Crm Email Router starts before ADFS, it fails to connect, and all the errors start occurring.
The CRM SDK has a little-known, but very useful set of projects called wsdlbasedproxies, which show how to connect to the CRM web services without using the .Net 4.0 assemblies.
When testing the project for claims, I found that it needs some code additions. The code as supplied (in SDK v 5.0.9) sets the credential.Windows property, but this fails with the error "The username is not provided. Specify username in ClientCredentials".