Woohoo.. Status changed to 'Approved' today. I never expected we'd be able to get it this fast.
EOI submitted: 31.03.2014 (165 points + job offer)
EOI selected: 02.04.2014
ITA received: 14.04.2014
ITA submitted: 17.04.2014
ITA received/accepted by INZ London branch: 22.04.2014 (a few days delay because of Easter)
Visa approved: 06.05.2014
So that's 5 weeks in total.
Thanks to everyone on this forum. All the info and help on this forum made it possible for us to be prepared to the max.