I'll take a look at `ScheduledObserver`.

Concerning delaying `onError`: Is that really useful? - Rx.NET doesn't seem to delay `onError`. [Here](http://www.introtorx.com/content/v1.0.10621.0/13_TimeShiftedSequences.html) it says: 
> It is worth noting that Delay will not time-shift OnError notifications. These will be propagated immediately. 

I agree, though, that this complicates things.