ConnectA2 was not a perfect app. Sometimes it would fail to connect and, after an update, it would constantly receive messages from +server saying "Unable to parse the resource". This messages were annoying, specially because one could several during a day. I once got 11 in two hours!
It also lacked certain characteristics from the real WhatsApp which, however, was never a problem for me. I mean, I was conscious ConnectA2 was NOT WhatsApp. So, expecting absolute equivalence was foolish. After all, I was using a FirefoxOS phone, not an android phone.
|LoquiIM...very similar to KDE's Kopete|
Once that ConnectA2 got seriously broken, I had to remove it and started using LoquiIM. This app lets one configure accounts on Facebook, Google Hangouts and, of course, WhatsApp. I only used it to access the WhatsApp network and found it quite efficient. However, every time WhatsApp released an app update, LoquiIM would fail. Of course, I was then using a developer phone. When I got the commercial FirefoxOS phone, LoquiIM was the only app that could access the WhatsApp network.
|OpenWapp, show me what you can do|
OpenWapp's design is very consistent with the rest of the apps on the FirefoxOS platform (HTML5?), so it feels very natural on the phone. However, I have noticed that it takes some time to display incoming messages.
For the time being, I will keep using OpenWapp. Let us see how it goes. If it performs poorly, I can always go back to LoquiIM or, if they fulfill their promise, I can give ConnectedIM a try.