"E-Chargers"

Has anyone tried these electric superchargers, and found real performance gains?

www.boosthead.com claims:
"Last month we sent an ESC™ to Street Concepts Magazine to install on a Ranger 2.5L 4-cyl show vehicle. You won't believe what they got from that truck! On a stock engine with headers, 3" exhaust, ECU modifications, and electric supercharger @ 6 psi, they took the Ranger from 122 stock whp to 223 whp! "

I know they can only provide short bursts of boost, which could be fun. I wanted to know how is air flow affected when the unit is not running though?