One of the near tragedies of contemporary Christianity is that we don't have a universally agreed upon translation of the Bible. For all its faults, the King James version once united the English-speaking Christian world with a common translation for all to memorize and quote together. The NIV has been the nearest thing for American evangelical Christians to a universal translation. But many have resisted it for years, choosing the NASB or the NKJV.
I prefer the ESV over the NIV because the original, precise ideas of the Biblical authors is much more transparent to the English reader. For example, one of the great words of the NT is "flesh" (Greek: sarx). When you read the book of Romans and Paul uses the word "sarx", the ESV will always translate it "flesh". So you can string together Paul's theology of the flesh as you read Romans for yourself. But if you have an NIV, you cannot tell when Paul is using the word "sarx". Sometimes it is translated "flesh", but at other times it is "sinful nature" or "man" or "what the nature desires" or "sinful man" or "the sinful mind". And those examples are strictly from Romans 8! Reading Romans 8 in the NIV, you could not know that Paul was developing a theology of the "flesh" by simply reading your Bible. So I find that the NIV does not sufficiently make the author's language accessible to the modern reader and is therefore not an ideal translation for serious Bible reading, preaching or studying. It is a very good translation for general Bible reading, but not careful study.
I love the New American Standard Bible (NAS). I grew up on it and most of my memory work has been done in it. The ESV is slightly superior to the NAS, in my estimation, because of literary excellence. The ESV pays more careful attention to structure and flow of the English language. The NAS accurately conveys the structure of the original language, but does not show concern for excellence in English literary form. So the NAS is a very "choppy" read, whereas the ESV flows with more beauty and simple elegance. There are however places where I do think the NAS captures the translation with more precision than the ESV. I noted this just this past Sunday as I preached on Romans 8:28. On the balance, I think ESV is more suitable for general use in preaching, reading, studying and memorizing than the NAS.
The ESV is superior to the New King James version simply because the NKJ is based on older manuscripts and is thus filled with translations that we know are incorrect. The NKJ translation team was aware of this and decided to put the more accurate renderings in the translation footnotes, but this is too cumbersome to use.
The ESV has quickly ascended into a place of prominence in Reformed churches in the US and the UK. Even some (self-described) Arminian megachurches, such as Prestonwood Baptist Church, have adopted it. So I am cautiously optimistic about the prospects of the ESV. I think it is worth entire congregations adopting and using together in unison as they learn God's Word. Will it one day overtake the NIV? That, I don't know. But I do think it is the best out there. If you want to get one for yourself, go here.