@chatto, no land problems. At least not that my weak mind remember
I have found that 23 is ok, but 24 is to be a little on the safe side.
BTW, it just occured to me, it also allow you to put in extra cards when sideboarding with no ill repercussions.
I tend to do that and so far i have not been mana screwed by running 61+ cards in duels two and three.