In my experience they are truly awful. They seem to have a genuine motivation in not posting your miles. My transactions have often gone 40+ days, I have submitted missing claims, eventually had email correspondence and in most cases after significant back and forth they post a partial amount. They will come up with all kinds of excuses why they cannot post the miles, and I end up giving up the fight, so ultimately they "win". I tend not to use the VS shopping portal now for exactly this reason.