Is room treatment a science?

Yes.

rhodes, well, both. (4mil$, 2000 butts in seats....generally not totally filled).....

When one enters that sphere, the acousticians start with scale models and 'mini-mics', trying to define where to start.

When the actual structure is nearly done is when the science butts into the art.  There's been spaces that looked great 'on paper' that sucked in reality and triggered major 'change orders' and compromises.

Sound in a given space, large or small, is generally a compromise.  In a home, unless one has built for the intended space, there will be trade-offs....and even with the 'built space'....MC alludes to that; he began with 'x', but lives with 'z' happily...

I'm approaching having to 'make that deal' in the near future.

But, for the time being, I just 'run what I've brung'...or have. *S*

It is a science and it’s not all about absorption. If you have corners, if you have 1st reflection points, then you will need treatments. If you have bass issues, after you have tried positioning the speakers with no cure, your corner absorption pieces will need to be fairly large, small panels only deal with higher frequencies. Also, diffusers can be both a diffuser and an absorber. IMO, work with GIK or ASC or both to get a good idea on what’s needed. Also, watch the Dennis foley YouTube videos on this subject, these guys are the experts

Yes, it’s a science. Reading the books and asking experts is always a good approach.

A few easy tips:
- “ slap echo” just means clapping your hands in center of room and
     listening for echo.
-if a ping pong ball will bounce off a surface so will sound.Glass 
 sucks.
- wool rugs work.
- book shelves on side walls with uneven books break up
  waves and work.
- try closing doors.

You can probably get a reasonable result that you are happy about by simple self administered methods or you can spend money up front and get an audio guy (they are normally involved with setting up home theatres) to come in and analyze the room for you.

The latter would certainly cost more up front, but would also prevent you trying things that didn't work, going down dead ends and spending money on the way. hard to know which would work out better and cheaper.