We have responded to your S2 headset problem in the other forum where you responded

About the other issues:
1. We actually haven't encountered this report from other users, at least not frequently. Try isolating the problem but testing it right after a reboot of the phone, with no other apps running. Does it still occur?
2.The photo delivery issues are known to us, but the specific scenario you described could be helpful to our support team in order to replicate the problem and hopefully fix it. Please report it here: http://bit.ly/ukGVJ0
3.
A. this feature is under development
B. Group chat is currently under development. Video calling is certainly on our list, but unfortunately we still don't know when exactly it will be ready.
C. We are considering to add an option to send just any file, but this also requires securing those files (so people won't use Viber to send malicious things), and so it could take more time than usually expected. Once we have news on that, I'll keep you posted.
D. Thanks for the suggestion. We'll take it into account

Thanks for all your reports and suggestions. We're really happy to see users like you, who are involved and contributing. This is how you can make a difference and help us shape Viber according to user demand

@ryuzaki_L -
We conduct strict testings in our labs with several devices and other than when making a call (when it is natural for the battery to be used), we did not come across any significant battery drain when Viber was simply running in the background. Furthermore, over the course of over 15 hours, on average the battery use was only 2%.

You can find additional information on tests performed by Viber users themselves, which show similar results, at:
http://whrl.pl/Rc0APn

@ryuzaki_L -
Not yet. It is a feature we are considering to add in the future, and we will let you know if we have any news about it