Ranked in these QuestionsQuestion Ranking
Pro Privacy focused
Tox uses military grade encryption and works completely peer-to-peer.
Pro Free and open source
The code is licensed under GPL (may change in the future) and is available on GitHub.
Pro Multiple front-ends for multiple platforms available
At the moment there is no official Tox client, but a selection of 32 and 64 clients for Windows, OS X, Linux and Android is available.
Con Early stages of development
Since Tox is relatively new, it has important features missing (like group video) and requires a proper code review before it can be deemed reliable and ready for everyday use.