You don't get kicked out of a movie while you are watching it?  I always do.  And I'm on a fast 15Mbps internet connection.  Searching the FyreTV forums, its a known bug with their servers that is supposed to be fixed in a few weeks.  
So far, I'm a little less than impressed with their responsiveness to fixing issues.  But its still beta, so no firm opinion yet.  However, they do need to fix the playback problems before I can actually use the box on a regular basis.  Right now, it just sits there most of the time.
-John