The Chromecast has been quite popular, so much so that it sold out soon after first becoming available. Granted, it was probably the price that attracted most people, as the wireless streaming device is still rather limited by the fact that it only works with a few select apps.
Still, Google is working on making it better and it's just released an updated software which fixes some issues with the device. Specifically, the discoverability of Chromecast devices should have improved.
Likewise, Google Play Movies streaming should be less erratic after the latest update. The upgrade is rolling out and will be installed automatically on your device as soon as it's available.
At the same time, Google has also updated the Google Cast SDK, now at version 1.0.1, though still in a preview. The update includes the libraries for both Android and iOS, as well as better documentation on the device, Chrome and the Android APIs.