Is there anyone else to whom we should be writing?

No. And commenting to ATF on this is just to document the strength of opposition to it for future court action or political solution.
Spitting into the wind, IMO. ATF examines these comments for information on the vulnerabilities of the hobby. It comes right back in our face sooner or later.
Probably best to send ATF the kind of content-free letter you get from politicians thanking you for your concern about some subject. +McG+

Send coppies to your Senators and Representative. Include a cover letter explaining what it is all about. Also note that the ATFE is ignoring real problems while wasting time harrasing harmless hobbiests. No, it will probably not do any good, but you never know.
Jim

What we need is something similar to the AMA rapid response center.
Mr. Mobley?

PLEASE write them. Encourage every rocketeer you know to write as well. They need to know how the rule will affect you AND your future spending.
A big problem is definitions. As WE know, a rocket motor is the archetypical PAD. My comments to BATFE involve showing government use and definitions of CAD/PAD which support inclusion of "rocket motors" under BATFE exemptions.
Here's a link with a government (Commerce) description of the CAD/PAD industry. Has some interesting definitions in the appendices.

You might also Google for "aircrew ejection propulsion systems propellant actuated device" and other CAD/PAD items.

The AMA response center seems like an efficient way to get the job done. I don't think writing a bunch of letters to the BATF is going to change anything, but making some of our representatives aware might. Unfortunately, it seems there is an anti-science mind set in the USA right now and some of the non-rocketeers that I speak to are pretty unsympathetic. I guess we live in a time when people will sacrifice anyone else's liberty if it makes them feel a little safer. Sad times. -> What we need is something similar to the AMA rapid response center. -> -> > > Send coppies to your Senators and Representative. Include a cover

The AMA response center seems like an efficient way to get the job done. I don't think writing a bunch of letters to the BATF is going to change anything, but making some of our representatives aware might. Unfortunately, it seems there is an anti-science mind set in the USA right now and some of the non-rocketeers that I speak to are pretty unsympathetic. I guess we live in a time when people will sacrifice anyone else's liberty if it makes them feel a little safer. Sad times. -> What we need is something similar to the AMA rapid response center. -> -> > > Send coppies to your Senators and Representative. Include a cover

They just want to take everything don't they? They take away rocketry, they want to take away music and arts (like RIAA going after people downloading online tabs), and they want to just commercialize anything that looks sellable. Whats next??

want to take away they want to just Dear Mr. Fu,
Please note that the name "Tai Fu" is trademarked by the Global Happy Fun Toy Company. As you are no doubt aware, GHFTC takes the issue of trademark violations very seriously, in order to protect its intellectual property rights and protect corporate profitability. We hereby demand that you immediately cease and desist all usage of the name "Tai Fu", or our attorneys will be forced to ensure compliance by seeking a court order of restraint.
Please accept the enclosed information pamphlet, "How to Legally Change Your Name", as a goodwill gesture on our part, to expedite your compliance with this demand. Also please accept the enclosed coupon, good for 10% off any Global Happy Fun Toy Company product at retailers nationwide.
Thank you for your cooperation, Sinist R. Hatchet, Attorney

Where? (looking around...)

Good catch. The document specifically defines "PROPELLANT ACTUATED DEVICE (PAD)" as "A rocket powered device releasing controlled propellant energy to perform a work function. This device provides propulsion for acceleration/deceleration, stabilization, divergence or deployment." A rocket motor releases "controlled propellant energy" to "perform a work function" (launching and recovering a rocket). It "provides propulsion for acceleration" during the ascent phase of the rocket's flight and uses an ejection charge for "deployment" of the rocket's recovery system.
-- Roger