This is a quick update with regard to CRM Web Service Toolkit. I had a chance to play around with the toolkit on CRM 2011 today, it turns out to be a surprise that the toolkit just works fine on CRM 2011 without requiring any modification. I tried to run all the unit tests that I developed in CrmServiceToolkitTest.aspx page, all tests have passed without any problems.
It's not me who has made this magic, but because CRM 2011 provided full backward compatibility with its web service interfaces. However, it's not my recommendation to use the CRM4 style web service interfaces, neither is this the best practice. But since CRM2011 SOAP Endpoint documentation is still under construction (shown below), I think it's not a terribly bad idea to keep using the CRM4 style web service interfaces for the time being, until the SOAP Endpoint details have been fully revealed.
Some may argue that we should all use CRM2011's REST endpoint instead since it's a new approach which may be more efficient, but be advised that the REST endpoint is not a full implementation of all CRM services. You are limited to only Create, Retrieve, Update, and Delete actions when you use REST endpoint.
I only tested on CRM2011 Beta, but I am relatively positive that the toolkit will work just fine for RC version, most likely the RTM version as well.