What kind of camera are you looking at, David and what kind of photography will you be using it for? There aren't too many 3MP cameras on store shelves these days so am I right in thinking that you're looking at a deal on a used or discontinued model? If so, there are other things you may want to consider.
Along with higher pixel counts, newer cameras often have improved image processing built in, better optics, and shorter "shutter lag" times than their predecessors. Even if you're just taking snapshots, shutter lag can be a real killer if you're takin' pics of the kids playing soccer or other kinds of action/candid shots. In situations like this, a ½-second is forever. Been there, suffered that, and missed many "moments."
But if you just need a casual 4x6 snapshot camera for subjects that aren't too much on the move, 3.1MP ought to do you just fine.