I don't understand why you'd roll all of your products into something that has a terrible user experience. I'm a long-time Google/Android user, and its just painful using Hangouts. I disabled it and switched to Telegram.
Those criticisms aren't about Telegram's UI as compared to Hangouts, though. At a minimum, your communication through Telegram is as secure as your communication through a google property.
Google Voice has never received a lot of attention or polish. (Disappointing to me, as a user since it was still named GrandCentral.) I hope it is integrated into Hangouts, because presumably it would see more improvement as part of such an important product than it sees now.
It is sad. I like Google Voice a lot. When it came out it was ahead of its time. When my phone is down I can use Voice to make calls for free (I am US based). I don't think Voice is available to international users yet? Have it?
The ability to call people using Google is already available on Hangout. If you upgrade your Gmail to use Hangout (I still have accounts that are not using Hangout) you will make calls via Hangout interface.
I agree with you, which is why I started Bolt (shameless plug: https://bolt.co). We are just getting started on our messaging app, which will be separate from our voice app due to the completely different use-cases.
The monolithic Hangouts app suffers from a bit of a Jack-of-all-trades problem. It's pretty good at four things, but not great at any single one.
It's really painful to see Telegram gaining popularity, when it has such glaring errors.
You should instead use OTR on Jabber (ChatSecure [3]), or TextSecure [4] (which now has an Internet delivery mechanism).
[0]: http://thoughtcrime.org/blog/telegram-crypto-challenge/
[1]: https://news.ycombinator.com/item?id=6936539
[2]: http://unhandledexpression.com/2013/12/17/telegram-stand-bac...
[3]: https://chatsecure.org/
[4]: https://play.google.com/store/apps/details?id=org.thoughtcri...