I think the speed is always a feature, but at the same time, caching always feels more interesting in terms of a proxy. For example, where I work, we're able to use one server and proxy massive amounts of traffic to a cluster of services. I know we paid for this tool and it has proved to be worth the money. That said, it does a great deal more than just caching where even if there were a faster caching solution, I'm not sure it would be worth paying for.

I hope that makes sense since simply stating "there are already those kinds of programs available" does mean that there isn't room for improvement. The evolution of lighttpd, nginx and cherokee all suggest that people found apache limiting in some way.

As for the service it did feel pretty darn fast, so kudos for that. More use cases or a more general caching proxy/load balancer might be something more people could consider worth paying for but that is just my own thought.

Good luck!