Their client list includes:
General Motors
EDS
The Office of Personnel Management (and I do recall exchanging email with a certain le femme fatale geekette about federal government opportunities. :) )
USDA
DOD
Dell
BlueCross Blueshield of Florida (which is one of the largest BlueCross BlueShield organizations. Since they adopted the usage of Brainbench, other state organizations are using it too. Anthem BCBS is another big user).
I've consulted with all of those organizations since 1998 and they have all heavily used Brainbench to screen and qualify candidates.
I have some compatriots at NASA, Wells Fargo and IBM who also have told me that they use Brainbench as one qualifying tool.
And the Brainbench certifications are usually have more real-world application of the technology questions than some of the vendor tests. So yes, it is a qualifying tool.
And like every other qualifying tool, it is just that, a tool. It doesn't address an engineer's skills at being a team member, taking direction, dealing with clients, resolving issues in a timely manner or the hundreds of other skills they need to be a success. It simply tells someone hiring an engineer that this engineer has enough knowledge and experience with the product to pass a test.
I recall when someone asked me if I had an A+ about 9 years ago and I actually laughed, as I had been in the field for over a decade then. Did I go out and get an A+, oh you betcha, since people doing hiring are often impressed (and that is another whole discussion!) by lil pieces of paper that say you are qualified.
But with the tests being free, I'd advise everyone to just peruse the offerings at the very least. Certainly beats watching dis-reality TV...