Bettertoser,
I like differing opinions. It helps us figure out the right choice for each of us.

I've been seeing osteopaths the past few years so that's probably where my train of thought is now coming from.
As a long-time TOSer, I know that my cervical ribs(or elongations of the C7 transverse processes, depending on who's reading my scans!) have, over time contributed to basically trashing my scalenes as well as my cervical spine. In my case, I think focusing on the cause, aka a Cervical rib resection, would do me almost no good whatsover because of all the downstream damage that's been done all my life. It's gone from a simple anatomical anomoly to an infinitely more complex one.

I tell people it's like being an alcoholic all your life and scarring up your liver. Just because you become sober and take the alcohol away doesn't mean your liver(and the rest of your body) is suddenly OK. It's the same with TOS.

Not quite the right analogy, but like sawxray said above, its about a balance of tension. That's what got me on the osteopathic tangent above. You may also want more than one read of a scan since it seems there's differing levels of knowledge of the balance of all those muscles in there.