Me go overboard with pipes? Nonsense. It's against my nature.
Good brushwork is the foundation of a balanced room. Pipes should be out of the way at all times or playerclipped(or nonsolid) to keep nauseating wallwalking problems at a minimum. I hate this "add pipes to make people say wow" crap. If it doesn't add to gameplay, keep it out of my movement space.
Putting pipes and greeble that don't have any purpose into your map is useless and kills FPS. Maps such as Karith Station use it in the way you should, by making the map pleasing to look at but never getting in your way. Instead of throwing in pipes everywhere uselessly, make it look like they serve a purpose. Have them go to a machine or something.
For example, pipes can also be used to show the direction a path is heading; adding more pipes that lead to one location might serve the players by telling them where the central power room is or something. Players could follow the pipes to reach it.
It's all about how you use aesthetically pleasing additions to a map to serve gameplay enhancements to the players.