It can't have anything to do with postcodes, as people I know in the same postcode have all recieved theirs over the course of the last week and a half.
I got mine last Wednesday, but my girlfriend hasn't gotten hers yet. I am actually worried she might not get it as she didn't have much of a taxable income last year, but as far as I know that shouldn't matter.
What shits me is people I know that have recieved 2, and I have heard cases of friends of friends recieving 3, and even 4 payments. Ridiculous.