Hardwood floors are just that - floors made out of exposed wood instead of concrete or what have you. Floors made of wood and covered by some other flooring aren't hardwood floors - the floor needs to be naked for all to see in order to qualify.
Having just moved from an apartment with linoleum in every room to one with hardwood floors in its only room, (well, ok, there's leopard-print tile in the kitchen. Seriously.) I can attest to hardwood's benefits.
- Hardwood floors are softer on the feet - they give a little with each step.
- They bounce light around the room, unlike carpet which absorbs it. Makes things less cave-like. A southern exposure is an added bonus.
- Hardwood doesn't sweat in the summer the way linoleum does.
- They're easier to clean. You don't need to own a vacuum cleaner. More importantly, you don't need to find somewhere to hide a vacuum cleaner when people come over. Well, I guess you could use it as a coat rack...
- Cats slide across them much easier than, say, concrete, raising your apartment's cuteness value by a few points.
- If your town ever floods you can pry up the floor and build a neat little raft. Try that with concrete.
- They're WAY classy.
Just to put things in perspective, there are a few downsides to hardwood:
- You know that thing I said up there about cats? Well, it isn't so cute when your floor slopes. I'm having a hard time staying at my desk right now because my chair keeps sliding backwards.
- They might not sweat, but they're damn cold in the winter.
- You've gotta be careful with drinks and stuff - hardwood stains if it's not varnished.
- Even if it is varnished, the floor tends to scratch easily.
Hardwood's a definite plus to your living space of choice. You can live without it but it just might make a standard apartment comfortable.