Say what you want about Apple, but onboarding for iMessages and Facetime did not require navigating a byzantine admin panel. I understand that Google Apps is a different beast, but there's something to be said for a chat service _just working_ in the way that iMessages does: you put in someone's phone number (or email) and if they are registered it works.
I recently tried to use my non-Google Jabber account with a friend who's on Gmail. Apparently Google no longer allows invites from non-Google Jabber accounts in the chat built into Gmail. Getting chat to work with a new contact even just between Gmail accounts would sometimes require some pretty opaque incantations -- and with external Jabber accounts it's even worse! There's no indication that your invite didn't go through to them, and I was never able to get his invite to come through to me.
tl;dr Based on my prior experience with Google and their IM products, I'm not convinced this could be an iMessage/Kik/WhatsApp replacement. Will my mom be able to use it?