The method (rainbow tables) is not new, no. There have been several efforts to produce a complete set of precomputed tables for GSM's A5/1 algorithm. What he did was finish the tables.

I haven't watched the video of the talk but I'm curious how he did it; I thought that some of the distributed-computation efforts were furthest along that path to completion.

Anyway, finishing and distributing the tables is not an insignificant achievement and makes A5/1 functionally much less secure, even if from a pure-math/academic perspective, the "break" occurred several years ago when the attack was first published.

Like many users and IT folks, I'm less interested in academic cryptography (though I find it interesting) than in the functional, in-the-wild side of things. The existence of a theoretical attack using precompute tables matters a lot more when those tables have actually been produced and distributed in a usable form. That's the case now, so that attack moves from being a theoretical one to a very real one.

The next step would be for someone to package the attack in the form of a script-kiddie-usable utility that would perform interception/decryption using an off-the-shelf GSM USB modem. I have my doubts that the mobile carriers and handset manufacturers will take any significant steps towards mitigation of A5/1 until it's not only broken in the academic and hacker communities, but the technology to intercept calls is in the hands of every moron with a casual interest in snooping. That seems to be how these things go; they'll drag their feet as long as possible, until the public pressure becomes unbearable.