The content of the ESV study Bible is still without equal. The new Zondervan NIV study Bible(D.A. Carson) comes close but falls short. The study notes, chapter introduction, maps and charts are fantastic. Wayne Grudem has wrote many articles located in the back on numerous topics that christians will find helpful. Christain ethics, cults, religions, interpreting the Bible and Biblical doctrine are just a few of the articles.
In regards to the Calfskin Study Bible, I was a little disappointed. I have a genuine leather ESV study Bible that I would give 5 stars. The calfskin came with some issues with the print. It is hard to go 10 pages without finding atleast one letter that is smudged on the page. This is disappointing considering this is a premium binding. However my cheaper ESV (genuine leather) lacks the print issue. My Calfskin issue is likley isolated, but disappointing consider the Bible is well over $100.