I like the UI and the execution. I don't know why it is limited to movies. The UI could easily be used for music too.
As for 'why it's limited': gotta focus on one thing at a time. We want to improve this one as much as possible, serve the community, improve content discovery/suggestion (that is personalized from your friends, not from some oracle rating stuff from 1 to 10)
We are (obviously) still refining our copy with movies.io, but when we're happy with it, there's still a lot on the plate: responsive design, releasing an API, mobile apps. RSS feeds are a killer feature: add a movie on your iPhone, it's downloaded when you go back home.
Once we have the "final" look of the website, we can apply the same design elements to finding TV Shows, etc. The sky's the limit, really. Oh, and one account for everything, of course.