The thing is, cutting through the bottom tube doesn't release the pedals. The bike is immobile while it's in the locked position. It would take quite a lot of effort I imagine to get it mobile again... I'd wager more effort that the average bike-thief is willing to go to. I agree that it's a little feature sparse. Some extra gears and decent brakes would definitely be a welcome addition.
From what I can tell from the info they give on the site, all that is blocking the pedals is the lower section of the bottom tube. Having a setting on the wheel nuts that locks them in place would be a better way to do this. Faced with the modern thieves arsenal of rotor saws and cutting torches, especially considering the msterials seem inferior to the standard U-lock. A lot of bike thievery has become about finding time, so they'll hit overnight lots or even put their own locks on and come back later. This design would work fine against a high school petty thief, but the pros who are stealing 500 bikes a year and fencing them wouldn't even be fazed. Now, I agree that the average bike thief would probably leave it, but any quality U-lock, or even chain lock could achieve the same. I just know that from what I've seen of it, I could steal it, and so people who are actually inclined and equipped could do so with less effort.