Hi Curious, I'm from Navi ESL. I was searching Google in the hopes of finding a review. I found this thread, and I just could not help but add my two cents to the conversation.

Well, NaviESL is operating for four years now and so far, we have helped a lot of aspiring English Teachers to fly to South Korea to do just that. We hire teachers the whole year, and we do not do an urgent hiring unless requested by the applicant. We are very careful in following our process, and preparing the documents for an E2 Visa takes very long, two months at least. Aside from that, we make sure that we keep in touch with the applicants and make sure that we are assisting them with the process as much as we can. And when every document is ready, we set a phone interview with the school and let them speak with a foreign teacher that's already teaching there. When that's done, we arrange their flight and we always make sure to meet them in the airport when they arrive. And while they are teaching in South Korea, we don't cut our communication with them. Leaving them with the best impression is very vital to us.

I hope this helps.