In looking at various C# Async CTP samples I see some async functions that return void, and others that return the non-generic Task. I can see why returning a Task<MyType> is useful to return data to the caller when the async operation completes, but the functions that I've seen that have a return type of Task never return any data. Why not return void?
Methods returning Task and Task<T> are composable - meaning that you can await them inside of an async method.
async methods returning void are not composable, but they do have two other important properties:
The second point is important when you're dealing with a context that maintains a count of outstanding asynchronous operations.
The ASP.NET context is one such context; if you use async Task methods without awaiting them from an async void method, then the ASP.NET request will be completed too early.
Another context is the AsyncContext I wrote for unit testing (available here) - the AsyncContext.Run method tracks the outstanding operation count and returns when it's zero.