While Ehrman is in fact a respected scholar within academic circles, his notoriety stems from his ability to take disputed issues within the academy and translate them into something that people outside of the academy care about. The problem is that Ehrman's presentation of the evidence and scholarship is often misleading and skewed. Of course, since the broader public has no way of knowing this, much of what he claims to be true has been accepted by those who are all too ready to question the New Testament, the canon of Scripture, and the development of the early church.
While there have been a number of books written to respond to Ehrman, I am most excited about this new website entitled The Ehrman Project. So far the webstie contains a number of short video clips on key subjects such as Evil and a Loving God (Alvin Plantinga), the Canon of Scripture (Ben Witherington III), Inerrancy (D.A. Carson), First-century Doctrine (Darrell Bock), Conspiracy (Ed Gravely), and Morality and Evil (Michael Kruger). This website has now become the go-to place for short, helpful and scholarly responses to the claims made by Ehrman.
On a related note, I am currently working my way through a book that responds to several claims made by Ehrman on a more academic level. Entitled The Heresy of Orthodoxy: How Contemporary Culture's Fascination with Diversity Has Reshaped Our Understanding of Early Christianity
If you are a pastor and are not familiar with these issues, you owe it to yourself and those to whom you minister to get up to speed on these matters. Use the website as a starting point, and then move on from there to this helpful read.