This the presentation that I gave during Real-time Conference Europe 2013 (http://realtimeconf.eu). It's a small summary of all the issues that you can have with websockets ranging from browsers to infrastructure to issues you cannot control such as the users environment.
The slides looks crap because they are generated to a pdf file so no fancy pancy animations that ties it all nicely together. Anyways, enjoy, read, learn and be awesome.