The Avid AAX Pack is a limited edition plug in bundle that comes with 18 AAX plug ins for Pro Tools, I use Pro Tools 10 and it works great with it. I have also heard that the Pro Tools 10 will work too. It can work with any of the AAX natives on a Mac or PC. This bundle is well worth the money because of all of the great and useful plug ins that it comes with.
Some of the plug ins that I really like are the softube passive active pack, sonnox inflator, kush audio UBK-1, Maag EQ4, Crane Song Phoenix II and the Avid ReVibe. There are many more though but those are some of the ones that I find myself using the most.
I have only owned this bundle for a week after purchasing it online, I was immediately emailed a link to download all of the plug ins and a link to download the manual. The download did take a long time, some of these plug ins are pretty big and depending on how fast your internet connection is it could take a long time to get them all.
If you are a Pro Tools lover/user than this bundle is a must have, I would first check with Avid to make sure that your version of Pro Tools will work with the AAX Pack. I did have some issues when trying to get Brainworx to install as a plug in but I just called Avid and they walked me through what I was doing wrong and then I had it up and running within minutes after being on the phone with them. They offer great support with installing and learning to use these plug ins. I am pretty sure they still have the tutorials online that are available for free to show you how to get the best out of each individual plug in.