Bug

This:

IAsyncObservable<int> src = AsyncObservable.Empty<int>().Delay(TimeSpan.FromSeconds(2));

behaves differently from this normal Rx equivalent:

IObservable<int> src = Observable.Empty<int>().Delay(TimeSpan.FromSeconds(2));

In both cases, the Empty<int>() operator completes immediately upon subscription. The normal Rx version will delay the OnCompleted call by 2 seconds, but the AsyncRx.NET version completes immediately. The AsyncRx.NET Delay only delays OnNextAsync calls, and not OnCompletedAsync calls.

AsyncRx.NET behaviour here should be consistent with normal Rx.NET.