I just finsihed a proof of concept with RTM bits and was surprised that for just out of the box lists, any query to listdata.svc was returning an error. In case anyone is stumbling or scratching their heads... there is an update for ADO.NET Data Services for .NET 3.5 SP1 that you need. Here is the download link:

http://www.microsoft.com/downloads/details.aspx?familyid=79d7f6f8-d6e9-4b8c-8640-17f89452148e&displaylang=en