GChat/Hangouts is not a social network, it's an IM app/service that uses your gmail account.I don't know anyone that uses Hangouts, especially those who have iDevices. It hasn't really taken off. With my friends I either Whatsapp, Facebook chat, Kik or iMessage (depending on their device). I love Gmail and I use it daily, but I don't really need Google's attempt at a social network.
iMessage to idevice coworkers/friends
hangout to android coworkers/friends.
*shrug* coworkers and college buddies and friends all seem to have retired AIM/Pidgin/Trillian etc and gravitated to this method due to the free, simplicity and universal nature of it.