1. The code is tiny with 90% of it dealing with RSS parsing and filtering. Using RX.NET wouldn't really simplify anything.

2. I wanted a library that I can integrate into my apps and run locally to avoid throttling, robots.txt and other BS Yahoo Pipes was suffering from.

I am also not a huge fan of RX... to put it mildly

Mind sharing why you don't like it ?

I personally like how it allows me to express complex high level operations cleanly. For example - I have a observable configuration variable that can come from different sources and the source change dynamically. I need to listen to latest source until a new one becomes active - in Rx I only need to push the new source trough IObservable<IObservable<ConfigurationValue>> and then use http://reactivex.io/documentation/operators/switch.html which returns IObservable<ConfigurationValue> which will push values from the latest source - Rx will handle unsubscribing from previous active source, synchronizing state and making sure everything is thread safe. And there are a bunch of operators like this that would be tedious and hard implement correctly with all the edge cases in a thread safe way - and here they are abstracted in to high level operators.