Oh very much so. What's been done with textsecure/signal is amazing.
I'm far more held back by not being able to get friends to switch from just chatting with Facebook app / Kik / Whatsapp etc than it being a browser app. I know I'm the outlier here. :)
Honestly, I don't know. I don't have one. But, for the price, I can see a lot of cool circumstances where a ChromeBook (or maybe Chromebox) could be very useful.