I can't remember where I read it, but Wendell Odom himself says that if you have the second edition you don't need to buy the third. He says that there isn't enough changed in the new one to really justify it. But he says if you don't have the second then definately buy the third. I was going to buy the third edition just for the simulator but it's just the lite edition which is very limited. Save your cash for hardware if you don't like sims.
Here's the link http://ccentskills.certskills.com/2011/10/04/need-to-buy/
Hi there Zed,
You should be fine with the second edition. Look on the cisco press site and download the errata for the book and you should be all set.
http://www.ciscopress.com/bookstore/product.asp?isbn=1587201836 (look for updates just under the "more information" bit)
Hope this helps,
Wendell officially states on this thread that second edition is fine for the exam. I passed ICND2 two weeks ago and used Second Edition books for 3 months of study:
The books and videos you are using are enough to pass the exam. However, you may consider reading other stuff like Sybex CCNA book and CBT Nuggets videos.
My CCNA Video Collection