I have also had a bad response from the Leonardo but only when using an external programmer.
See my post Arduino V 1.0 and later
Uploading with the bootloader gives a good O/P and no issues, but a programmer seems a bad idea with the Leonardo.
My Freetronics Elevens, ether2560's,even a 2560 mega breakout ex Sparkfun are all fine, all but the Leonardos (I have 3 - they all misbehave when programmed with a programmer).
The Leonardo behaves the same way with XP and Win7 when using a programmer, so it surely can't be that all the OS's and drivers are corrupt, but moreso an issue in the Leonardo architecture.
I'm harping on progammers but I need ISP uploads not usb.
But we try different MCU's, then find one that works for what we want it to do. It's the same with PC's, you buy one that can do the job and not all PC's will work the same, as we all know.
So we need to work out which MCU will do a particular job - so you might end up with a few different types.