Are HERF Guns Useless?

I've been doing a little searching around the internet for information on HERF (High Energy Radio Frequency) Guns and have been kind of surprised by what I've found. Over the years I read some magazine articles which referenced HERF technology and made it out to be really awesome with claims of stalling running cars and possibly damaging their electronics or destroying computers from well outside the building they are in.

The reality is slightly less impressive from what I can tell. With the HERF Guns a hobbyist could make, you can stall an idling car or crash (not permanently damage) a computer from maybe 3 meters away. Forget about stalling out a moving car on the freeway. Now, you could substantially increase the power but you would need far more expensive equipment and you better keep your testicles in a Faraday cage if you plan to be nearby while using it.

I'm hesitant to declare HERF Guns useless as I could come up with possible uses for them but unless I'm wrong you can forget any badass dreams of ditching the cops with one. It would be interesting to experiment with one to see if my judgments are correct but the personal health risks involved probably mean I never will... Input from anyone with first hand experience is definitely welcome.