penders - 8:02 am on Oct 24, 2013 (gmt 0)
Give it a few minutes. ;) I've found the auto-update check can occur at any time - not just when it first starts.
...I realise today that I am now on Opera 17.0.1241.45 ! I have been automagically updated at some point and I was unaware!
I think this was actually as a result of my previous download/install on Oct 8, it would have downloaded Opera 17 at that time, not Opera 16. (Op 17 was released on Oct 8 [opera.com]) The update is only installed after you restart Opera, but there is no prompt to do so.
I have since had another minor update (17.01241.45 to 17.10241.53) and it seems that it is only that I now have UAC enabled (I previously had this turned off for a while) that I get to see the "Terms and Conditions" Window (behind the UAC dialog) - but you don't appear to have to accept this? The only user interaction is the initial "There is an update, install now?" prompt. (Although, as stated, it doesn't actually appear to "install now"... it "downloads now" and installs later.)