what is annoying for me is unreliability of delivery of messages. some never get to target phone! Simple scenario - I send messages 1, 2, 3. All three gets delivery on target phone (double gray "hook"), first one gets to be read (hooks turn blue), second doesn't, third does. Country - Switzerland. Both platforms - android.
Just one step away from moving away from whatsapp, considering competition offers sometimes much more (ie viber - emoticons, childish but lovely way to talk to my gf :))
I haven't seen this, but I'm on Windows Phone, so perhaps it's platform-specific?