I have a Kickflash, and I'm quite happy with it.
I had some problems in the start (the latest firmware didn't quite like my particular A4000T) but I got great and fast support from Jens Schönfeld/Individual Computers and CoyoteFlux (programmers of the CoyoteFlash tool), and it's working now.
As for the reduction in boot time, it's very individual. Basically, the boot time is reduced by the amount of time that passes between the setpatch reboot and when the computer starts booting again.
Go ahead, you won't regret it.
-Paul
