we have hardwood/tile in most of our downstairs living space. i bought those alphabet cushy floor tiles and created a small play area. when cade started crawling, it didn't matter after that. he crawled all over them and didn't seem bothered - i think his knees got calloused!when they start walking, barefoot is best (slippery socks). when it is cold, i put cade in slippers w/ rubber soles or at least have socks w/ grippers on them (you could prob make some w/ puff paint). i just bought an 8x10 rug and that's where we play now. (got tired of the brightly colored alphabet tiles!). previously, we had a seagrass rug which wasn't much softer!
fortunately, cade has never hit his head, etc on the floors. he usu hit the coffee table (the legs, not even the corners!). ii moved our coffee table b/c i'm about to buy a leather ottoman...no bumps since! i'd just buy some more rugs if you're worried about it.
i'd briefly leave cade for a split sec if i left the room.