I played through the Eden Prime mission and watched his back story, but is the rest of his inclusion in the main story similar to Kasumi or Zaeed?
He's more similar to your normal squad members than the previous DLC party members were.
He has interactive dialog sequences just like normal squadmates.
He has scenes where he interacts with other crew members over the comms.
You can also talk to him aboard the Citadel where you can use a Paragon interrupt to convince him to give an inspirational speech to an Assari, Turian, and Hanar.
Javik has some unique dialogue so you should talk to him between missions and have him in your squad more often. Especially on the Priority: Thessia mission - you will learn some pretty interesting stuff about the Asari only he can tell you.
Javik is your only source to the "previous cycle" and he can give you a different perspective on things. IMO he has a lot more "significance" than just the Eden Prime mission.