Under ASP.NET MVC are you supposed to pick up QueryString params the same way you do in ASP.NET WebForms? or does the [AcceptVerbs(HttpVerbs.Get)] declaration get used somehow?
You can always use Request.QueryString
collection like Web forms, but you can also make MVC handle them and pass them as parameters. This is the suggested way as it's easier and it will validate input data type automatically.
Query string parameters can be accepted simply by using an argument on the action - i.e.
public ActionResult Foo(string someValue, int someOtherValue) {...}
which will accept a query like .../someroute?someValue=abc&someOtherValue=123
Other than that, you can look at the request directly for more control.
I recommend using the ValueProvider property of the controller, much in the way that UpdateModel/TryUpdateModel do to extract the route, query, and form parameters required. This will keep your method signatures from potentially growing very large and being subject to frequent change. It also makes it a little easier to test since you can supply a ValueProvider to the controller during unit tests.