The major differences in text occur in the Gospels, although there are some significant differences in the epistles as well.
The two most easily notable differences between the Byzantine text/Textus Receptus are the lengthy passage about the woman caught in adultery and the final pericope of the Gospel of St. Mark. To the NIV editors' credit, they did not omit them entirely, as do many modern translations, nor do they stick the text into a footnote. But the editors do mark them off and say that "the oldest and most reliable manuscripts do not contain this passage" -- or something like that. Oldest, yes. Most reliable? A *very* debatable matter of opinion.
Keep in mind that the consensus opinion amongst modern textual scholars is that St. Mark's Gospel is the olest Gospel. So go look at that passage at the end of St. Mark, and see what is missing from "the oldest Gospel."
I've got to run, but just Google "KJV only" and you will find quite a few websites that detail the textual differences between the critical Greek text and the KJV. I was completely unaware that this movement existed in the fundamentalist world. I thought that only traditional Anglicans and Orthodox even cared about the KJV anymore.
Needless to say, I do not care for the shrill tone of many of these websites, nor do I agree with much of the theology, etc... But if you just want to have lists of the differences in texts, you'll find them very easily on these sites. The KJV only people also believe that the Hebrew texts used in the KJV are superior, but I haven't studied that issue at all, since we are LXX people. The Catholics might care, since I suspect that the Hebrew texts that St. Jerome used may be more like the KJV texts than are those used today -- but given the strict uniformity of the Masoretic tradition, I can't imagine that there would be many differences in any event.
On readability, you are right that there are archaisms. You might enjoy the "Third Millenium Bible," which has removed true archaisms (i.e. if words have actually changed in meaning -- like "conversation" and "prevent"), changed some awkward sentence constructions, etc... There are also recently available epistle and Gospel books put out in the Orthodox world which supposedly do the same thing, but I haven't perused them enough to recommend them withh confidence.
But I will say this also. KJV English is actually more understandable on the whole (especially for the non-highly educated) than is NIV English. Testing has placed KJV English at about the 5th grade level. The NIV tests out at about 8th grade (I learned this from a KJV only site, but I do believe it to be true, based on my intimate familiarity with both translations -- I used the NIV exclusively for many years as a Protestant.)
So dive in and use the KJV -- read it aloud, get a glossary of archaisms from a KJV only site (some other gems I have found on those sites for which I am grateful.) The water is fine, better than you would think when you just dip your toe in!
LOLOL. In what parochial school was that test conducted?
I used the NIV exclusively for many years as a Protestant.
I'm not surprised.
Good memory, Agrarian. In the body of the text, after verse 8 and before verse 9, my Bible inserts "The earliest manuscripts and some other ancient witnesses do not have Mark 16:9-20". But the whole section is there, red letters and all. :) I didn't know that was a KJV difference from many other versions. Even though some of the verses are a little weird sounding, I have always considered the passage to be fully scriptural.
Thank you for all of your comments on the KJV. I did Google as you suggested and found some sites that I will look into. It was funny that most on the first page were actually anti-KJV-only sites. They shouldn't get to be listed first. :)