A quick heads up to those of you still rocking a first-generation Chromecast and have been patiently awaiting the firmware update that will enable Spotify support — it's here. Just a couple taps and you'll be sending the latest from [insert artist/band Phil hasn't heard of] from the Wild Wild World Wide Web down to your dongle.
The change required a a firmware update — I'm now on 1.16.44433, for what it's worth. If you're not seeing the update yet, you can try these instructions. Streaming to the new Chromecast Audio, however, will still require a Spotify Premium subscription.