** Updated 12/2/2012 **
Just upgraded to iTunes 22.214.171.124 and the issue has not improved at all. I reenabled my Wi-Fi sync and it seemed to take a while longer before the AppleMobileDeviceHelper.exe started consuming CPU like crazy (about 5-6 hours) but consume it did. Also the iPhone and iPad completely don’t see the server so Wi-Fi sync is still broken. I’ve disabled that mode of syncing again. I suppose it will have to be an iTunes 12 fix?
** End Update **
So, it turns out that disabling sync over Wi-Fi eliminates the high CPU consumption issues with both the AppleMobileDeviceHelper.exe and ATH.exe
This is relatively painless to do since the Wi-Fi sync stopped working with the 10.7 iTunes update on the Windows 7 (64 bit) release anyway.
I’ll leave this disabled until the next iTunes update. It’s a shame because the Wi-Fi sync is a pretty slick feature.
To disable, just plug your iDevice into your computer and, in iTunes on the Summary page, uncheck the “Sync with this computer over Wi-Fi” checkbox and click apply