When Plex announced that it would be an official Chromecast partner, I knew that I had to get ahold of one. On Christmas day, I jumped onto Amazon and ordered one for £35.
I had been using Plex for about 4 month before this, however I only had access to a very limited set of features due to using it as a DLNA device. I could browse the media (thumbnail and title) and play, and that was about it.
Getting the Chromecast has unlocked a lot more features that have made watching TV shows and Movies a whole lot nicer.
For example, I use trakt.tv extensivly, and with a simple plugin, Plex automatically sends what I am watching to Trakt. This means I can keep track of what I am watching, and even tell Plex to filter only "Unwatched" episodes/movies. This now works with stuff I watch on my TV thanks to their Chromecast support, so I no longer have to worry about marking things as watched manually with an app.
Another great advantage is being able to control your TV with basically any device in the house. I can pick my Mac up, choose a TV show and start watching, and then pick my phone up and turn the volume down on the TV. This makes everything seamless and much nicer to use.
Because it's all going though Plex, it also means that I could stop watching something half way through, and pick up where I left off on my phone. For example, I could watch QI on the way home on the Metro, and finish watching an episode on my TV using Chromecast when I got in.
If you use Plex, and have not yet got a Chromecast, then I really recommmend it. It has made watching media a lot nicer experience overall. And if you do not use Plex, then try it out!
Let me know how you get on in the comments.