I think the biggest controversy of the FV thing is a lack of Christian love being shown by those who think they know something, but who have never gotten it from the beginning. I don't really see the men who were first accused of FV theology writing anything lately, but I do see them being attacked without any real evidence and with strong vitriol.
The whole affair, from the very beginning, was fueled by envy, hatred, and really bad scholarship. From where I sit, the whole thing has been handled like a bunch of seminary students sitting around the cafeteria lunch table arguing and bickering about silly little topics they don't really know anything about.
The only theological point that is open to question is in the area of what has been called Federal Vision theology (btw--I don't think there is any such thing as FV theology), is the issue of what exactly is going on when we talk about branches that do not produce fruit being cut of the vine, which is Christ (John 15). Some folks want to say the branches are not really branches, but what are they? Jesus called them branches. He even said that the people listening to him at the time were branches. But what does that mean in the sense of eternity?
Did the branches that were part of the vine have salvation and then lose it? Were they never filled with the sap from the main vine itself? Why, if they were part of the vine, getting sap, did they not produce fruit?
We have the same problem with the branches that were cut off the tree because of unbelief in Romans 11. The whole point of the passage is that we may not become proud of our status in the tree because previous branches were cut off because of that kind of pride. But those branches must have really been part of the tree before being cut off, or the warning has no punch. But if they were really part of the tree, how can they be cut off? And more how, if we have been grafted in, can we be then cut off?
In my view the best explanation is that the branches are people who are covenantally part of the vine. They experience all the blessings and joy that members of the covenant community enjoy. They are part of Christ, are his body, etc. but when they do not produce fruit or have faith, they are cut off. They do not automatically have salvation, from an individual standpoint, but if they remain in the vine and produce fruit, they will be saved as part of Christ, in the last day.
How it all works is a mystery. You can have assurance of salvation because you are a member in good standing in the church and you are a member because of faith in Christ's atoning work on your behalf. God saves us because of what Christ has done for us, not because of what or how we believe. But our faith in Christ does make us live in a certain way and that way is to produce fruit.
Still, I think the worst travesty in all of this is the lack of love being expressed by those who are arguing and bickering and who are trying to destroy peoples lives and careers over it. This is especially true when those who are shouting the loudest seem to be doing it so they can become somebody in the Christian world.
I hope this helps.