Seems to be working okay. The Sony authored Messaging Smart Extension still shows SMS even though they are now displayed inside Hangouts.
I'm using WatchIt! now to capture all other notifications and pushing them to the device. Seems to work great so far.
Android user since 1.5 Cupcake
HTC Dream, Motorola Milestone, Samsung Nexus S, Samsung Galaxy Note i717, Sony Xperia Go, LG Nexus 4, LG Nexus 7
LG Nexus 5 (Telus), Sony SmartWatch 2, Samsung Note 10.1 (2014) Edition, Moto G (Wind)