For starters
- provide apis to track custom exceptions though try catch
- enables you to track errors for cross origin scripts
- support minified code through source map
- track the users so its easy to understand the impact of problem.
- supports modular logging same as server side
- track custom events
- search though the data
And much more
Check out documentation to know more
http://developers.debuggify.net/docs/#!/guide/simple
http://developers.debuggify.net/docs/#!/guide/advance