No, its only if you want to chat with them as a 'Hangout' that they'll need the app. SMS get sent through it normally. Personally I'd rather they'd kept SMS as a separate app!!
Nexus 5 in hand - good to have a fully working phone again! First thoughts:
* Feels better in the hand with the slightly curved back and being rubberised it will not have the Nexus 4s suicidal tendencies to be able to fall off any flat surface.
* Annoyingly the screen protector has Nexus 5...
I have the Nexus 4 but having dropped it in the bath (yes I know!) the touchscreen doesn't work at the bottom so decided to get the new Nexus 5. Apparently its been sitting on a vehicle at Gatwick since 2am waiting to go for delivery but it hasn't left yet. Come on, I need my new phone!!!