I had thought that the Lutherans (LCMS only, ELCA don't even qualify as heretics anymore) had a pretty good grasp on it, until I started noticing the extra crud they were adding on to the list of things one "must believe" to be a proper Christian. I've gone over that before so I won't belabor it now, Young Earth Creationism and what I consider a mistaken reading of Romans 13 and their overly restrictive rules on who can share the Eucharist are on the top of my list.
Then there was the Roman Catholic Church, who actually do claim to have "All of the Truth" about the gospel. They even claim that since Jesus stated that the gates of hell shall not prevail against the church that everything the church teaches must therefore be TRUE. I'm pretty sure they have misinterpreted what Jesus was getting at there :-) It wouldn't be so bad if they did not seem to go out of their way to make up new and increasingly strange "Marian Dogmas." I did my very best to accept those, since I was convinced that Jesus did want his church to be united and the only possible candidate for that is the Roman church. I even bought a book by Tim Staples called "Behold Your Mother" that was supposed to explain the Marian teachings in a way that would be easier to accept. I actually threw that nice hard-bound book into the recycling bin at work to make sure no one else read it. It was really the thing that convinced me that they have no leg to stand on in their teachings about Mary! Staples takes the thinnest of biblical justifications and expands them into chapter after chapter of wild speculation. In any case I came to conclude that Rome too did not have all Truth.
Which left me with my old Anglican ideas, where one gets the best of Catholic and Lutheran thoughts, in my opinion anyway, and fine liturgical services, mostly, and a bit wider idea of what the church is, all baptized Christians are welcome to participate in the Eucharist. As I said before, the ACNA is more loyal to the traditional understanding of scripture than the ECUSA... but of course they don't even claim to be the exclusive repository of all truth, but they do their best to figure it out, and I now have concluded that this is probably the best anyone can do.
So, Quid est veritas? Jesus, and him crucified. But not any one group of believers in Him.