The biggest question I have about the Joseph Smith translation, is whether or not it was EVER meant to be given to the public. Since he said it was not to be unsealed until it arrived in Zion, then I would have been very hesitant to let it out to the Church at large, especially knowing that it would then be available to the general public.
Much of the Doctrine and Covenants, as well as the Book of Moses, came from his study and work on the translation of the Bible. So, much of our advanced understanding of eternal principles comes from this work as well. However, much of the work of the critics also comes from this same source.
While I love the JST, It really makes me wonder if Joseph Smith III didn't really mess things up by allowing it to go forth.
I've been studying the JST/IV for half a year now. It has really helped me A LOT! It is the most wonderful and most complete bible translation we can have at this time. At least in my humble opinion.
If ya'll want to know whether or not it is important to study the JST, check out the current priesthood manual on Joseph Smith. I don't know the page in the English manual (It's p. 71 in German, so it can't be to far from that in English ), it's chapter 4 the part where it says 'scriptures give us joy, comfort and wisdom' etc. There it says the Kingdom of God cannot progress without the Book of Mormon and the publication of the JST. (quote is from History of the Church 4:187). Hence we can see the need for studying the JST. Personally, I by now started to use the JST exclusively because I think no bible translation can bring me closer to the truth than Joseph's translation. Just my thoughts....
I have never regarded the JST as a full blown bible review/correction and bring it in line with the original first penned manuscript. He would not have had the time either. He has corrected verses that are currently seriously questioned as being authentic. There are some beautiful stories with great messages that are just not found in the oldest sources available today. Still great stories but is it scripture? Does it matter?
So to me, I have always viewed the JST as Joseph going through the scriptures and anything he found that was not doctrinally correct, to make it doctrinally sound. I don't think he was concerned or questioned whether this really was inserted by some person 500 years later or not. But his making the pieces of the puzzle all fit makes a lot more sense to me and adds great value and side stepping at the same time the minefield of what actually is authentic or not. Keep in mind that we only know 10 words fore sure that is/are authentic in the NT. All the rest originated 100-300 years AD They found over 200,000 variations in the NT. so go figure.
Why don't we use it as a church if we know it has been inspired in its' translation by Joseph Smith?