What are some alternatives?
When comparing gReader and Serendipity by Spotify, you can also consider the following products
Inoreader - Dive into your favorite content. The content reader for power users who want to save time.
Last.fm - The world's largest online music service. Listen online, find out more about your favourite artists, and get music recommendations, only at Last.fm
Pandora - Pandora Radio is a free (ad-supported) internet radio founded in 2000.
PaperOak - The best free Rss reader
Google Play Music - Free radio for everything you do. Store 50,000 tracks from your personal collection. Subscribe for on-demand access to 40 million songs and offline listening.