I attended an interview with an ECO on October 4 at VFS Islamabad. She said that she'd make a decision the same day and I got the email too. However, I have yet to be contacted by the VFS to collect my passport. How long does it usually take? I have to go away for a week for a reporting assignment (I'm a journalist) so being a little anxious.
Today is 7 October and you had your interview on 4 October. That means a full two days have passed, it's not enough time.
The processing time for the British mission at Islamabad is shown in this screen capture...
So with a fair wind you should have something back by next Thursday, 13 October.
And they guarantee you'll hear from them by 4 November.