I have an Intuos2 that I've been using since 2004 and only had to buy replacement nibs ONCE in 8 years. I've had my current nib in this stylus for almost 2 years now. It's flattened out, but works okay.
In the new Intuos5, you can't even replace the overlay sheet because it uses some kind of electronics inside and is built into the tablet (for the touch version). I love the touch features, but it's not worth it at all if i have to worry about replacing nibs or scratching the "irreplaceable" surface. Ugg, apparently, they're not even selling overlay sheets for Wacoms anymore. I guess it's back to finding acrylic sheets from plastic companies and cutting toothpicks down for nibs. Thanks wacom, for nothing.
Also that gave me a few ideas as well. I'm sure there's some kind of spray coating that can be applied to the surface to make it really smooth again. Failing that and having PORUS go out of business, maybe using that "clear document cover" talked about in the first link. Or if everything fails, you could figure out what kind of plastic the overlay is made from and get the materials and "pour" out your own. And there's always some nice high grit sand paper...
I hate being cynical, I really do. Yay for hope and stuff. :P