Just got my Mega Pack today and tried the upgrade process... I followed the instructions carefully, however, the logo screen does not come on when inserting the rocket cable while holding the start button (handheld is switched off). However, I am getting the rapidly flashing blue light and after releasing the start button, the switching blue/red lights indicating the upgrade is downloading (according to the rocket cable anyway). I waited about 10 minutes and got no indication that the upgrade was finished (instructions say it takes 5 - 7 minutes, then the system will reboot) so I disconnected the cable. My system did not recognize the SD card after this, however, so I am repeating the process (still with no flashing logo or "upgrade in progress" display on the screen). I checked my system firmware and its 370.
So does this seem to be defective SD cards and/or rocket cables? Or are some handhelds just not compatible with the new product?