You've already noted the primary difference in wall tile application vs. flooring. If the wall tile backing is reasonably sound the job will turn out, however, especially in older homes, the floor must be almost perfect. Loose nails must be re-secured, Floor boards that squeak indicate boards that are "working" and must be stablized. This usually involves installing another layer of OSB or plywood. Then, the floor measurements present a problem. Most flooring tile is 12 inches square or more, rather than the 4 inch square standard wall tile. This means planning the layout so as to minimize the neccessary cuts. The water cooled cutting saw is an art to master in itself. It can certainly be done by an accomplished DIYer, but is not for the faint of heart or one with little patience...Best of luck!