Can you still option+click to update IPCC in the new build of iTunes?
EDIT: From what I've been hearing... the OPTION+CLICK/SHIFT+CLICK has been patched in iTunes. If you want to keep your Cellular Data Network panel and whatever else a 5.0 IPCC file enables... MAKE SURE TO have the 5.0 IPCC already on your iPhone before you install this. Otherwise, I don't think you'll be able to update it from 3.5.
EDIT: From what I've been hearing... the OPTION+CLICK/SHIFT+CLICK has been patched in iTunes. If you want to keep your Cellular Data Network panel and whatever else a 5.0 IPCC file enables... MAKE SURE TO have the 5.0 IPCC already on your iPhone before you install this. Otherwise, I don't think you'll be able to update it from 3.5.