I took the time to look up a few of these verses in my NIV Bible:
Matthew 12:47 -- removed in the footnotes
Matthew 12:47 is in my NIV version (footnotes say, "some manuscripts do not have verse 47)
Matthew 17:21 -- COMPLETELY removed [also deleted from the Jehovah's Witness "Bible"]. What are you NIV readers missing?
"Howbeit this kind goeth not out but by prayer and fasting."
Matthew 17:21 is in my NIV version's footnotes "but this kind does not go out except by prayer and fasting"
Matthew 18:11 -- COMPLETELY removed [also deleted from the Jehovah's Witness "Bible"]. What are you NIV readers missing?
"For the Son of man is come to save that which was lost."
Matthew 18:11 is in my NIV version's footnotes "The Son of Man came to save what was lost."
Matthew 21:44 -- removed in the footnotes
Matthew 21:44 is in my NIV version; the footnotes say, "some manuscripts do not have verse 44."
Matthew 23:14 -- COMPLETELY removed [also deleted from the Jehovah's Witness "Bible"]. What are you NIV readers missing?
"Woe unto you, scribes and Pharisees, hypocrites! for ye devour widows' houses, and for a pretence make long prayer: therefore ye shall receive the greater damnation."
Matthew 23:14 is in my NIV version's footnotes, "Woe to you, teachers of the law and Pharisees, you hypocrites! You devour widows' houses and for a show make lengthy prayers. Therefore you will be punished more severely."
Mark 7:16 -- COMPLETELY removed [also deleted from the Jehovah's Witness "Bible"]. What are you NIV readers missing?
"If any man have ears to hear, let him hear."
Mark 7:16 is in my NIV version's footnotes, "If anyone has ears to hear, let him hear."
Mark 9:44 -- COMPLETELY removed [also deleted from the Jehovah's Witness "Bible"]. What are you NIV readers missing?
"Where their worm dieth not, and the fire is not quenched."
Mark 9:44 is in my NIV version's footnotes
Mark 9:46 -- COMPLETELY removed [also deleted from the Jehovah's Witness "Bible"]. What are you NIV readers missing?
"Where their worm dieth not, and the fire is not quenched."
Mark 9:46 is in my NIV version's footnotes
Well...I could go on. I use the "Mom's Devotional Bible New International Version", Zondervan Publishing House, (c) 1996 by The Zondervan Corporation (The Holy Bible, New International Version (r) Copyright 1973, 1978, 1984 by International Bible Society). In the front is a very lengthy Preface explaining who, what, when, where, why and how the translation was made. I have read the Preface twice and was personally satisfied with its explanations.
For those interested, here is a copy of the Preface:
http://www.ibsstl.org/niv/background.php