reply to TheSMJ
Re: Sanding/refinishing oak floor a DIY job? Could fill the 1/4" holes with hard-wood dowel - I think that much putty would be far too obvious, myself.
The tack-strips, either putty, or just leave them. I'd be tempted to do the later... Trying to fill and match, could easily make them MORE visible, rather then less.
As for the discolouration - I'm going to say (and I'm a phone guy by trade, not a flooring guy, so take it with the appropriate grain of salt) - that the dirt and staining is pretty ground into the finish, and sanding/refinishing is the way to go. The boards look to be in good shape, it's just the finish that's wore out.
Try a good cleaner (murphy's oil soap) and some elbow grease, but if that doesn't do it, you're probably looking at a strip and re-finish.