Except that Apache (and Passenger) don't just start up N worker processes - they can dynamically allocate them as the need arises. Perhaps this is less important for a site like github, which can plan exactly how many to use, but if you have more than one site on the same server, it's really convenient, and, IMO, makes Passenger the best choice for deploying Rails for most people.

So it appears as if this setup replicates a small portion of what Apache does without all the bells and whistles.