I take it in fruit juice / milk, Crazy :-)
Shak, I don't believe in long term use of vitamins, and generally I'd say that my diet is more than adequate for normal vitamin / mineral requirements.
However, I do think that pregnancy / post-birth is different. The toll it takes on your body is immense, and I think some people underestimate that.
My body is actually broken since last time (I get stuff ankles and hobble for 5 or so minutes after getting up and my tail bone 'pops' if I sit in the wrong / any position for very long) so god knows how I am internally!
I know that when we were both - DH and I - seriously sleep deprived, taking iron really seemed to help perk us up.
So, for me it's needs must right now, with a view to going back to a normal healthy diet once I finish breast feeding DC2, or 6 months post partum, whichever is later.