To my mind old fashioned hardwood floors are far more trouble than they are worth, especially now that we have better and better Engineered Floors available. An engineered floor is not a cheap plastic laminate on masonite floating floor. It is a very stable, usually pre-finished, real massive hardwood floor that is glued up either from pieces and veneers of dried hard wood, or all veneers like a plywood. Either way is far more stable than single pieces of hardwood.
The most common type has a core of short pieces of solid hardwood-- no warping or twisting. The bottom is a rough veneer which helps to stabilize the product. The top of the quality products is a very thick veneer that goes almost to the toung and hence could be sanded, but with proper maintenance you never will need to sand it.
The multiple coat aluminum oxide factory finish is harder than anything that could ever be put on over a freshly sanded floor. Many years from now if you do see the first signs of wear you could use the Verathane Renewal system (or whatever has replaced it by the time you get around to needing it) to simply refresh the finish and you never will need to sand it. If you do get a gouge, it will only expose real hardwood below, so a bit of stain and finish and it is repaired.
The best have a click groove system, which means that you could staple it down, you could glue it down, you could float it and glue the joints together (but with no need for clamps as the click lock will hold it while the glue dries), or you could completely float it with no glue nor nails and then lift it up one board at a time either for repairs or to take it with you when you move. Imagine a hardwood floor you could place in an apartment you are renting, and take the floor with you when you move!
A more recent innovation is the click groove in the end of each board -- meaning that even if you leave it floating, it will never open on the ends, a common problem with unglued click lock products. Another advantage of a click together floor is that you can't get it out of line -- it doesn't take any skill or experience to install it.
Why would we want to float a floor rather than nail it down? Cracks and sound! All floors expand and contract somewhat and if the boards are nailed down, in the winter time small cracks will appear between boards. With a floating floor, all the expansion and contraction happens on the edges of the room and the floor remains one uninterrupted sheet.
This could cause problems in a very large room with heavy furniture and wide humidity swings as the heavy furniture could stop the movement of the floor and something could open up in the middle. Placing the boards in this room in the opposite direction with the heavy furniture sitting on the ends of boards, not on the edges of boards could solve the problem because real wood doesn't shrink much in length, only in width. You do need to realize that if you live in extreme climates, like the humidity of Vancouver and Halifax or the dryness of Calgary, it is critically important to open the packages and acclimatize the boards to the room they are going into -- as long as 6 to 7 weeks. In fact that is a good idea with any flooring in any climate to open the boxes in the proper room at least 4 weeks prior to installation. That gets the boards to the moisture level of the house and to their "acclimatized" expansion or contraction, avoiding surprises later.
When you nail a floor down, sound and walking impact will be transmitted to the room below. With a floating floor, a good sound insulating under-pad can make it quieter than it was before you put the hardwood down. Understand that there is a wide variety of quality in underpads, some only prevent the clicking sound of the boards being walked on, others are truely soundproofing pads for the room or appartment below.
Whether making it simple enough to be able to do it yourself with just a saw to cut boards short, or whether radically cutting the labour costs of having a professional install it (including avoiding the dust of sanding and odours of finishing), I really do recommend prefinished engineered style floor boards.