Actually, they go back to the original text. Check out the explanation for the net bible in Bible.org
I know the King James isn't the first. Neither is the model T. But it was the first "popular." And I consider no translation "perfect" compared to other translations. ALthough I do consider some just plain flawed, like the Readers Digest version, for example.
The King James is just one of many accurate translations, and someone needs to translate it into understandable english.
see this link.
http://www.biblebelievers.com/Vance5.html
The King James is the 7th translation of God's words in English.
Hence, it lines up with Psa.12:6
the words of the lord are pure words, as silver tried in a furnace of earth, purified seven times
As for being understandable, anyone can understand it if they take the time to read it.