IMO it's a pretty crap addition to a very solid chassis. The Fighter is a solid character class, it can survive having a bad subclass added to it and still be fine.
Comparing it to the Bladesinger, it is bad. The Bladesinger gives us a fully functioning wizard with some solid and viable melee options. The EK gives us a fully functional fighter, with comparatively rather lame magical options. With the Bladesinger I feel that I have everything I want in a magic-leaning Gish, with the EK I don't feel that I am a complete melee-leaning Gish. That being said, I don't think it is healthy to compare things to the Bladesinger, it is a very sweet class.
Personally I would take any other Gish option over the EK, but it does fit the bill if you wanted a guy in platemail, which the others cannot do easily.
If you want a guy who is a badass plate wearer who uses magic to do extra damage or defense, then a Paladin seems a lot better at it. Looking at the EKs spells vs the Paladin, I am not sure that the EK is getting a good deal with his extra abilities balancing out that spell casting and smiting.