Dude, take a look at what's happening here.
The "security hole" in question here is basically the same deal as you have with every other service where you can transfer your service to a new device. You know, you buy a new phone, then want to continue using your IM or whatever on the new phone... but with the new phone you'd also get to negotiate new encryption keys. And that means that all messages still in the queue would be lost, because they have been encrypted with your old key.
That's the whole "exploit" here.
There's plenty of reasons to distrust WhatsApp and even more reasons to avoid it like the plague, not the least of which being that it hands all data over to FB despite first claiming and vowing that it would never do that.
If THIS is your reason to distrust WhatsApp, you have bigger problems.