I still don't understand what is difficulty in learning to use
Windows Phone. I have tried all OS (feature phone,
Android, WP, iOS and BB), and for me it takes few minutes to start operting that phone even if I am using that phone for first time (may be I am extra smart

). I have in past helped people setup their Android phones even though I had never used Android phone till then.
My opinion is Windows Phone could be easiest to operate for old people as it has big live tiles on home screen. So it can be easily selected by touching. Besides tiles size can be changed from small squares to full wide tile. And based on usage on needed app tiles can be pinned on home screen (e.g. Phone, Contacts, SMS). For incoming calls, it displays quite large numbers/characters so its easily readable for old people.