Many churches have gone to using the NKJV as the standard for church service and in written articles.
This parallel Bible is excellent for those who use the KJV as the standard scriptures for preaching/teaching and where the NKJV is the standard in his/her church.
One thing that is very interesting is noticing the differences in KJV/NKJV quotes. In some cases there are as many as 6 changes per page. For those who are interested in biblical criticism, this is an excellent tool to show that the NKJV is more of the revised text type than many think.
Another neat feature in the NKJV is that many of the NT footnotes, annotated as NU or M, are the texts usually used in the NIV and the NRSV or related Bibles.
So for the money, you are getting not only a parallel of the NKJV but also of the other texts.
I recommend it.