My server (and I believe others) are doing specific parsing on the query parameters rather than trying to let the model binders in webapi do that part.
You will highly likely need to have a custom one anyway so that you can handle the search modifiers/prefixes which are defined in the spec here
Also the standard .net serializers need to be replaced with custom ones as noted in this stack overflow article
Hope this is of some use.
You may want to look at how this is done in the open source Spark Server by Furore
(Just highlighting the XML Formatter, but all the rest of the code is there too)