Is Instapaper merely adequate, or is it better? Would it have been that much better if it was constructed in Rails?
IIRC, Instapaper's a PHP application. I could have mentioned a larger site, but Instapaper was probably a better example, since it's quite popular with HNers.
Well, I hate Rails so that wouldn't be my first comparison.
But yes, it would probably be more easily maintainable if written in a better language, and the developers would be able to add new features more quickly.
To comment based on your metaphor, the problem is not that the screwdriver/hammer is ugly. It's that the grip doesn't feel right and it's unbalanced. You can turn the screw and drive the nail, but it takes more effort and might leave your hands scraped up.