I have been importing and selling the Earvana nut for several years now.
I have fitted it to many instruments and find it really good.
Personally I prefer it to the Buzz Feiten system as it only requires you to set up and tune your instrument as you normally do it.
It looks like you have intonation set at both ends of the string as the nut has a stagger for each string

Some players think that the staggered nut looks odd at first but are then so pleased with the improved in-tune nature of their guitar that they dont mind.
For Gibson type guitars there is a "shelf nut version that just drops into place
See below

The Buzz Feiten and Earvana systems both try to tackle the same problem.
What they try to do is to solve the problem of notes being slightly sharp near to the nut and as you go up the neck through proper compensation.
Sharp notes will stop the chord ringing true and especially on the 3rd of any chord, which the ear is more sensitive to.
I find that after using these systems you can play chords that normally dont sound good with overdrive like a C and it sounds much sweeter . It also allows you to move from chord to chord with them all sunding more in tune.
The diagram below shows a before and after test done with a strobe tuner with an Earvana nut being fitted to a guitar.
