To each their own...
As far as the E-Force and the warrenty, I absolutely love the E-Forces. I did the first two 2010 SS E-Force kits for Route 66 Motorsports two years ago, and the first 4.6L 3v E-Force about the same time. I have always been impressed with their output for the pressure level, and the throtte response is very impressive with these kits, which lead to a very fun car to drive on the street. Now I doubt you'll be breaking any dyno records with one of these superchargers compared to a Kenne Bell, but I think the perspective buyers of each brand of superchargers are different as well.
As far as the warrenty, they have three different packages that cover different amounts and different mileage/year. We have yet to have to make a claim, but from talking to their sales rep, it's a no brainer. There's a seal on the pulley for the supercharger, and as long as that seal isn't broken, they'll cover it if it was installed at an authorized installer and tuned by the installer if the pre programed programmer was not used.
Here's another E-Force set up I tuned for LCPD last week as well. It has way too much gear to make it anything but a burn out queen. http://www.youtube.com/watch?v=RaY5R...2&feature=plcp