The regular Shelby Series 1 is about as fast as the Z06 Corvette, and the supercharged version has about the same acceleration as a lightly modded Gen II, or SRT-10 Viper (1/4 mile in 12.1@ 120MPH).
If the supercharged models were priced the same as the Viper then they would have sold MANY more of them. But despite the nice styling, there is a bit of a kit car look to the cars, and most people don't know what they are, other than a sporty convertible.
Shelby got great performance numbers one the supercharged Shelby Series 2 of 0-60mph in just 3.2 seconds and a standing quarter mile of 11.3 secs at 126mph.
But who knows how much the boost was cranked, and if they used drag radials.
There are rumors of Shelby coming out with a special run of 427 supercharged Series One cars in 2004, but who knows.
-Dean.