It's true that the basic concept of appear.in is pretty similar to a lot of other WebRTC prototypes made (like the ones you mention). However we are trying to turn appear.in into a commercial product that will be continually improved and adapted to users' needs (that will likely change over time). It is very easy to get a working prototype up and running (appear.in started as a summer project, and three interns made the first working prototype in two weeks: http://comoyo.github.io/blog/2013/08/05/video-meetings-in-th...), but getting it to work smoothly in all kinds of situations, on all kinds of networks and handling bugs (which occur frequently) is another story. Not to mention keeping the product up to date and making use of all the improvements that are made in the different browsers.
We think that widespread adoption of a service like this will only be achieved if the service "just works" and is adapted to users' needs through constant development, and also through building a living brand that people love. We are currently a team of 8 working full-time on this, not only programming, but also with marketing, design & user testing.