When I hear that "it only took me x time", I typically wonder how much of the work is original ingenuity compared to successfully 'gluing' an app together with pre-made libraries. It's more impressive to me when you say "Look at this desk I built in two weeks from trees in my backyard" than "Look at this IKEA desk I assembled in 4 hours" if you'll pardon the crude analogy.
To be fair, both can be equally impressive, and there is no reason to reinvent the wheel unless you can make it better.
I don't think this analogy really carries over to software development. I think being able to develop quality code in X time even using libraries is a great demonstration of experience.
It just depends. When I see that it's a real-time chat room built on top of node.js, it doesn't really interest me. A chat room is basically the Hello World of node.js/socket.io, and I think I built my first one in a matter of hours. But, other things usually entice me to click the link. I think I click just about every Show HN link that I see, though. :P
I'm more concerned with what it is, not how long it took. I am a firm believer in "build half/launch early" etc, but to me greatness is measured on an absolute scale.
I generally wonder whether they mean a 24 hour period, or ~24 hours spread over several evenings and weekends.
The second option wouldn't include the extra dozens of hours mentally solving any problems in the shower or on the way to work...
My reaction is usually "I don't care how long it took to build, I care how good it is!"
generally I think, this implementation time only. ie, the design decisions have already been made, and problems have been solved.
Generally, I think: "Great, you implemented a feature and registered a domain for it."