Go ahead and laugh, I'm standing by it! :-)
Taken as a whole, the KJV uses significantly fewer words, less complex words, and simpler sentence structure than does the NIV. This is particularly true in the Gospels and in the OT. The epistles are often difficult to make simple in any translation -- because the originals aren't simple. The KJV specifically had in view its public reading to a public that was not highly educated. I grew up around simple country people, many of whom hadn't been to high school, but who understood the KJV perfectly well for the most part. Pastors made sure to correct the obvious misunderstandings, and all was well.
In general, when the KJV is convoluted or obscure, it is because the original language is convoluted or obscure (I am here speaking to the Greek only -- I couldn't read Hebrew to save my life.) Many modern translations have a knack for making simple things falsely complex, and complex things falsely simple...
C.S. Lewis once wrote about the updating of the BCP. One of the changes made was that there was a prayer that asked that our rulers would apply the law "indifferently." This was updated to "impartial." Lewis asked a few villagers what they thought "indifferently" meant, and they replied that they supposed it meant that it meant that it didn't make any difference to the ruler one way or another how things turned out -- which is a pretty good definition of impartial. On the other hand, they had no idea what "impartial" meant.
I grew up on the KJV and know many, many verses and passages in it by heart as a result. When I was a senior in high school, our pastor recommended switching to the NIV for private study, and our pew Bibles were changed to the NIV a couple of years later. I used it through college and early grad school, changing back to the KJV during my Anglican years. I can now hardly get through a paragraph of it anymore... It is banal in the extreme, IMHO.
KJV has many conceptual errors. One, for sure is the ending of the Lord's prayer with the "from evil" vice from "the evil one." Another that comes to mind is "be therefore perfect..." vice "become [future tense] perfect..."
I hate to think of all the misconceptions created through KJV in the minds of people who read the NT "cold" (i.e. not in the context of the Holy Tradition).