If I were using Shakespere as a guide knowing God and living my life, I would want it rewritten into the most understandable language possible. Since it is only entertainment, I don't mind that it is difficult to understand.
However, I have been to several "updated" versions of his plays and find them every bit as good as the originals, because it isn't just flowery wording that makes Shakespeare great, it is character development, dialogue, scene set up and an insight to the human condition that only Shakespeare had. The modern version of Julius Caeser is wonderful, because when you understand the language, you can feel the drama, the intrigue, the emotions of the characters without them having to be overacted like traditional Shakespeare has to be to get the message across. Cassius's fear of Caesar comes out, Brutus's love for him appears and his final betrayal of his best friend is protrayed with all the angst it should have. The actors are free to act and don't have to try to convey emotions through over-grand gestures or exagerated tones of voice that they used to do because the audience wouldn't be able to understand the words.
Dost thou knowest mine heart? (translation: Do you understand what I am saying?) Elizabethe's verbat t'is'n't eft. (it isn't easy to understand Elizabethan language) T'is more than an esperence atwixt we and they. (no one has spoken like that for a long time) T'is near bavin anon. (it's nearly useless now)
Plus, word meaning have changed so much since then that they don't even make sense in context.
"Avoid" meant to empty or to throw away something, not to stay away from somewhere like it does now. "Awful" meant to be in the act of worship. "Abide" meant to complete a journey, not to stay home like it does now. It is easy to take wrong meanings because of the way the definitions have changed. Without an elizabethan dictionary, I don't know how anyone can be sure they understand what the KJV is really saying.
As for the hymns, check your hymnbooks. Any hymn written before 1900 was probably updated by 1950. Rock of Ages has had three language updates, and it is very unlikely that your hymnal has the original version. "How Great Thou Art" has had two updates that I know of. Open your hymnal and check the words against an old hymnal from before 1875 and you will see that although they are similar, they are not the original words.
I dig-you-good-den. (I wish you a good evening, in Shakespearean English)