If you're writing configuration to manage your assets you're doing it wrong.
silentrob.me> comes with a production ready web server, and watches your files by default
If it's watching your files, it's not production ready.
Care to expand on that? What are the drawbacks?
It sounds to me that they've integrated a site build system into their webserver. What's wrong with that?
Are you going to get latency spikes when it decides a file has changed? What happens if the syntax for some, but not all, of the files is wrong? Deploying to a production webserver is something that wants to be as explicit and simple as possible; complex tasks like compilation/substitution of these script files belong earlier in the pipeline.
Harp doesn't watch your files. It lazily compiles as requests come in and stores the results in an LRU cache.