Don't get me wrong - I realise it is a rather new device, and I am aware that majority of n9 devices don't have this problem - but as long as this problem occurs, without any obvious reason (not any excessive cpu usage process seen in terminal 'top'), I'm entitled to moan about it... at least that...
what's interesting - it seems that last ( of maybe 10) reboot really helped, and now with skype on I get 24mA consumption... let's hope it remains like that...

EDIT: @Vaterix 'real' push, using ms exchange, not checking periodically checking through mail.app