In our case, we needed something that is both secure and competitive in comparison to mass market solutions in terms of speed, working on weak connections and usability.
Disclaimer: I work for Telegram.
Usability, however, is a different beast. You must compromise security to make a chat application appeal to "regular" users. Still, this is a trade-off that can be clearly communicated to the user and to developers, and does not require a custom crypto protocol. You can achieve the same effects with using existing and tested libraries.
Edit: Disclaimer: I am the developer of the yaxim Android XMPP client and the operator of the public yax.im XMPP server (both available at http://yax.im).
Now that google is killing talk in favour of proprietary hangouts, I predict it'll be a while before I'm a serious xmpp user again.
Sadly it's very hard to push process changes when one are in the minority in a group... Thanks for the reminder though, it does look like it full-fills most of my needs (and fixes annoyances I've encountered with other android clients).
Knowing this, I hope you can appreciate why the burden of proof on your unproven team and approach is fairly high.