When I took my class on the Book of Acts at LU, the textbook that I used was from a well-known, Calvinistic scholar from Dallas Theological Seminary named Darrell Bock. Dr. Bock is a top rank textual scholar whose opinion should carry with it a great deal of weight on textual/translational issues. I mention all of this because he has a couple of posts defending the new NIV 2011 which may be helpful in this debate. Articles that one may find helpful in weeding through the mess and mass of criticisms that have been launched at the NIV 2011.
Here is an example of why I believe we should be a little slow to pull the trigger on the NIV 2011, without hearing both sides of the issue. In Acts 15:40, the ESV renders the verse as such;
but Paul chose Silas and departed, having been commended by the brothers to the grace of the Lord. (ESV, Acts 15:40)
Now, notice the NET Bible (New English Translation) rendering of this verse;
but Paul chose Silas and set out, commended to the grace of the Lord by the brothers and sisters. (Acts 15:40, NET)
On first glance, one may cry fowl and scream, “Gender Neutral.” However, this is simply not the case, as seen in the textual note which goes along with this verse;
118tn Grk “by the brothers.” Here it it is highly probable that the entire congregation is in view, not just men, so the translation “brothers and sisters” has been used for the plural ἀδελφῶν (adelfwn),.
My point is, there was a perfectly good reason why the NET translators added the word “sisters” into their translation. Granted, it is not the historic way this verse has been translated per English translations. But, it is accurate per the Greek plural used by Luke and it must be noted that the translators of the NET had to make a tough decision regarding this textual issue. This just could be the case regarding the NIV 2011 as well in some or many cases. I have not personally seen the translation as of yet so I hesitate to comment any further.