A few interesting spots I ran across while reading my ESV as my pastor preached from the NIV.
Acts 15:10-11: KJV - ESV - NIV
I seem to remember verse 11 being a point of contention anyway, because some translations say that we "are" saved (NIV, for example) while others say we "will be" saved (KJV, ESV, others). But the thing that actually caught my eye was that my pastor said that the "even as they" referred to the "fathers", not the "disciples." Many of the translations in my e-Sword leave it ambiguous, but the ESV by saying "will" has made it less ambiguous than the KJV and even the NIV (in the ESV it pretty explicitly refers to the disciples, not the fathers), which would seem to go against their stated goal of being ambiguous where the text is ambiguous. Or maybe it's not that ambiguous in the original and all those other translations got it wrong.
Romans 1:17: KJV - ESV - NIV
Most translations say "from faith to faith" in this verse. Seems like the ESV, RSV, and NRSV are in lonely territory with their use of "for" there: ESV "from faith for faith" RSV & etc. "through faith for faith." Seems like the "to" would indicate a timing concept or a sort of travel metaphor, and the "for" indicates a reason that something is done. (Notice, however, that both the ESV and the NIV have the more traditional rendering in a footnote.)
I wish I could get inside the translators' heads and find out why they settled on what they did in these kinds of cases. They may be right, but to find out WHY they did certain things would be fascinating!