I take a multi-vit! In any case, I've done Thurs-Sun this week then I'm off till next Friday when it's back to days. I tend to stagger when I get in bed on my days off so I go to bed progressively earlier/later depending on if I'm doing nights/day so it never feels like a massive adjustment.
The social life thing with nights is the worst, I'd never do it full-time, even though work days are no different from nights (get up, go to work, come home, go to bed): can't pop on the DLR to go to Stratford or Poplar for lunch at night! Do it for 3-4 days, then there's 4-6 days to do whatever. Some weeks it's week-days I get off, others weekends which is great as things like shopping or going to places in London is less hectic in the week, and obviously nights out are better at the weekend.