Ok, I've been beating my keyboard for the last half hour and finally figured out a way to get AMDS for iTunes 8.2 installed and working on my machine. In my case, the .msi was throwing up an error about needing to have SP2 installed (which I do), preventing me from installing the drivers. Here's what I did:
First:
1. Download Microsoft Orca if you don't already have it
2. Extract AppleMobileDeviceSupport64.msi file from iTunes64.exe (v8.2)
3. Uninstall previous version of Apple Mobile Device Support
Next:
1. Open AppleMobileDeviceSupport64.msi with Orca
2. Select "LaunchCondition" from the left pane. In the right pane you should see the condition "(VersionNT=501 And ServicePackLevel>=2) Or VersionNT>=600"
3. Edit this condition to read:
(VersionNT=501 And ServicePackLevel<=1) Or VersionNT>=501
4. Save and exit Orca. Run AppleMobileDeviceSupport64.msi and it should now work!
Hope this helps