Bottom Line: it's not secure, it's convenient
The only lesson in this article and the commentary is that ANY wireless transmission (including IR) is not secure. It is, however, convenient.
Let's look at this realistically. You have a wireless transmission that has a range of 10 meters. So anyone that is trying to eavesdrop on it has to be close enough to get clear reception of the signal. OK, if there's someone lurking behind your living room couch, chase them out! Second, the reception needs to be done while something "useful" is being typed - like your bank logon password. Since this doesn't happen all the time, the eavesdropper probably needs to either relay or record the keystroke data in order to post-process it for interesting bits.
The effort to do this is fairly large: unless you have a specific, high-value target in mind, it's much, MUCH cheaper to just buy the data from a black-market data broker.
On the other hand, a reasonably high-value target would be a bank branch or similar location that uses wireless keyboards. Or Larry Ellison's house.
And finally: if you can get within 10 meters of your "target", you can probably get a data logger dongle directly onto their keyboard connection ANYWAY.
Everything in life has a risk associated with it. For the average home user, this one is right up there with being killed by terrorists using a two-part liquid explosive device on an airplane. Go warp yourselves up with tinfoil-lined bubble wrap again.
(BTW, it's a good article, John. I didn't know that 27MHz keyboards used a key to limit cross-talk with other similar devices, and it just MIGHT be useful to warn those high-value targets.)