Another thing to consider is the amount of strike and sparge water you use can have a big effect on efficiency. I use BeerSmith too and I love it, but lately i've noticed that the volumes of water it calculates for strike and sparge water don't seem to be optimal; in my experiance, they're on the low side. Lately i've looked at these calculations and have added about half a gallon more water than it tells me and that seems to help. If you're fly-sparging, a lot depends on when you stop the sparge. The optimal grist-water ratio should vary a bit by style and the equipment you're using, but like i said, in my experience the BeerSmith calculations have resulted in mashes that are too thick.